text:
Jobs indirectly related to the meat business
According to the Vanijja Sutta on Right Livelihood:

"Monks, a lay follower should not engage in five types of business.
  Which five? Business in weapons, business in human beings, business
  in meat, business in intoxicants, and business in poison.

The first precept forbids taking of a life.
The ability to freeze, store, transport and sell meat later was not possible in the time of the Buddha.
Questions:

Is it ok for someone observing the first precept and Right Livelihood, to be a frozen meat retailer, supplier or importer selling frozen meat sourced from elsewhere (but is not involved with the actual farming and slaughter of animals)?
Is it ok for someone observing the first precept and Right Livelihood, to work as a cashier or general worker in a supermarket or hypermarket (e.g. Tesco, Target or Aldi) that sells many things including frozen meat?
Is it ok for someone observing the first precept and Right Livelihood, to work as an employee in a logistics company (like FedEx) that stores and transports all types of products including frozen meat?
Is it ok for someone observing the first precept and Right Livelihood, to work as a chef or waiter in a restaurant that serves meat dishes, using only frozen meat (no live animals)?

I closed this as a duplicate of Can lay people be involved in the weapons business? because the other topic already has answers which examine the limits and intent of the same sutta.

@ChrisW I would argue that it doesn't necessarily have to relate to a sutta and I doubt it is so much a duplicate that it needs to be closed. Also, you engaged the question yourself with an awesome comment(IMHO) to an answer  a long time before you closed the question.  Also, it says the question is an exact duplicate but obviously the answer I wrote for this question can't just be pasted into the other question. I wasted a lot of time. -Metta New Year

@Lowbrow I reopened it so you can post your answer.

The reason the Buddha suggested we abstain from certain things is not because of the morality of the actions themselves, but because of the effect these actions have on our minds.
The fact that you are even asking this question illustrates there is some sort of mental suffering/inner conflict that has arrisen. This is the suffering we are attempting to avoid by abstaining from specific actions. This is what the Buddha warned us of.
You are always free to do whatever you wish! I would just suggest you not do something that brings you suffering.

The very fact of you asking that question conveys what kind of business meat business is.
I would like to present it from Thich Nhat Hanh perspective on Right livelihood (Mahayana):

In forgetfulness, we may separate ourselves from the butcher, thinking
  his livelihood is wrong, while ours is right. However, if we didn't
  eat meat, the butcher wouldn't kill or kill less.

It is better not to do any meat business at all, or deal with meat at all. We can do better, and not at expense of other beings; humans are omnivores, killing and participating in killing is not required.

I realise this was down voted because it doesn't conform to dogma. However, allegedly we should not take anything for granted in Buddhism. In developed countries, eating meat has no other value than selfish taste pleasure; refraining from not eating meat is volition that makes a difference by reducing demand on meat and therefore, directly cutting down suffering. Another aspect is changing collective consciousness and environment, what I noticed is that when people see that one refrains from eating meat, they quickly adopt the same stance and this further works toward alleviating suffering

And I am not referring there to meat by offering, but the act of purchasing meat, which implies that butcher does, in the long term, kills animals for us, since we create demand.

I've seen a (non-Mahayana) argument that avoiding (the purchase of) meat doesn't alleviate suffering, e.g. because mice and so on die when plant-crops are pest-controlled and harvested (instead of animals dying when they're slaughtered for meat). Even so I don't disagree with you.

Yes I have heard this argument. Scale of animal death and suffering from pest control versus deliberate industrial slaughter in conventional way is negligible. All the animals coming from a conventional industrial way require giant amounts of grain and crops. Note that this doubles the impact due to inefficiency of such meat growth and fact that all these grains would go to us instead - straight. On top of that, we gravitate towards better and more humane pest control systems these days that become non-harming, with bigger resource use. Yet, not many people decide on these due to greed.

My answers to
Question 1.
No.
Question 2
Yes
Question 3
Yes
If you are selling meat, you are directly involved in the business of buying meat from people who kill the animals.
If you work as a cashier or logistics, you have nothing to do with the killing of animals.

This answer is the same as the answer of Dhammadhatu that was scored down thrice by the sīlabbata-parāmāsa-sangha.

The chosing of words here: a lay follower should not engage in five types of business is very conductive and wise.
"Engage" -> three doors of conduct, mental, by signs or direct by body.
When ever you may get the feeling to engage, to be involved, to feel not well with it, try to change and fix it. It's in most cases not really possible to generalize useful for many in certain details, but the main objectives are to find freedom from remorse by keeping precepts and once they grow to a matter of heart and leave the level of outwardly "rituals" or justification of all variants, the wise and conductive way is to follow ones heart and uprightness. Whether such is made by changing whole things or by changing ones also executed level of engagement in a non-denying way, a non-hypocratical but honest way, might be also different case by case.
At least, once aware and clear of effects, mental approve, not to speak of enjoying benefit based on suffering of others, althought not ordered by signs or words, not done bodily and direct, such mental kamma has effects.
That is why it is suggests but not often forwarded, since difficult from most, or certain "dangerous" to lose persons favors: "a lay follower should not engage in five types of business".
Especially in SE-Asia it is very seldom straight and un-flowered forwarded.
Maybe a sample is useful to make it more alive: There is a young family making their live by selling pork is soup and the householder drives daily his motorbike through the villages to sell "fresh" meat from pigs. They usually love giving and when ever on alms coming till their village, not only meeting the husband on his hurry selling drive, they would joyfully offer some of the noodle soup. It has needed a very long time till my person was able to "give a little back", to meet the proper occasion so that they would be able to listen, propably understand. Some days ago the mother of the pair was visiting, and while joyful prepearing alms was moaning on and on "Ohh, steedy ill... permanent sick..." After the round after the meal, the house was crossed again and turning now around, asking "who is permanent sick" my person was explained that the young householder was subject - not much wondering - and got invited to sit down and possible help. So they have been carefully been taught about the issue of livelihood and the protection of silas in regard of sickness and livespan. Not surprising the couple would have prevered to hear a blessing or what ever "miracle" and not much of joy to hear that, yet nevertheless listening... My person had not met the meat driver since this day and did not came till their house since this occation. May it not only be a "the Dhamma is right" but also have possible turned to a longtime better.
One needs to know and understand that sure 40% and more people are actually engaged in meat - or animal trade business and the rest of 55%in other un-lucky trade. Why should the reallity in the west or modern world be much different? Only because the whole way from killing till the serving of food is more defuse and not so easy traceable does not mean that "reality" and less care, or not seeing an alternative, not able to let go of certain things, needed to let go, are not different even more worse.
While people observe things here in the neigborhood here, "reality" enters the homes over there via TV, youtube or SE... who's today not merely just an employee rather than business owner... who is informed and aware, free to choose his ways or not.
What about all the modern occupations and harmful trades, deriving issues?
Step to more remorseless livelihood as soon as issues are traced. There is much more benefit of a seldom to gained live is taking on the "lower" and "simplier", not so material benefical ways to earn a living and to be possible just a servant, house keeper or helper, cleaner... what ever. Its good to be modest and prefer highest Protections:

To have much learning, to be skillful in handicraft,[8] well-trained in discipline,[9] and to be of good speech[10] — this is the greatest blessing.
To support mother and father, to cherish wife and children, and to be engaged in peaceful occupation — this is the greatest blessing.
To be generous in giving, to be righteous in conduct,[11] to help one's relatives, and to be blameless in action — this is the greatest blessing.

There is nothing wrong in being gifted a blessed to be able to accumulate a lot of wealth proper and in rightous earned ways, but it is not wise at all to let go of ones virtue and life at easy for what ever amount of outwardly gain.
"Lesser (of certain things outwardly) is more (peace, happiness and ease).", a prover tells.
Good results require certain hard work: that's the Noble truth of Suffering, and there is just one way out and proper conduct to continue with most possible ease, if still wishing to wander on, take and pay, before or afterwards.
Nearly 24:00 and the sound of hunters gun is to be heared from the near other mountains forests, sometimes just the barking of the deers is the loudest... screeming after a spouse...
Make good use of possible highest blessings gained and give causes so that such effects are not only seeked but gained, as sure as birth is followed by death.

"From an inconceivable beginning comes transmigration. A beginning point is not evident, though beings hindered by ignorance and fettered by craving are transmigrating & wandering on. What do you think, monks? Which is greater, the blood you have shed from having your heads cut off while transmigrating & wandering this long, long time, or the water in the four great oceans?"... The blood you have shed when, being water buffaloes, you had your water buffalo-heads cut off... when, being rams, you had your ram-heads cut off... when, being goats, you had your goat-heads cut off... when, being deer, you had your deer-heads cut off... when, being chickens, you had your chicken-heads cut off... when, being pigs, you had your pig-heads cut off: Long has this been greater than the water in the four great oceans.... "Why is that? From an inconceivable beginning comes transmigration. A beginning point is not evident, though beings hindered by ignorance and fettered by craving are transmigrating & wandering on. Long have you thus experienced stress, experienced pain, experienced loss, swelling the cemeteries — enough to become disenchanted with all fabrications, enough to become dispassionate, enough to be released."
That is what the Blessed One said. Gratified, the monks delighted in the Blessed One's words. And while this explanation was being given, the minds of the thirty monks from Pava — through lack of clinging — were released from fermentations.

[Note: This is a gift of Dhamma and not meant for commercial purpose or other low wordily gains by means of trade and exchange.]

The direct translation of Right Livelhood (by Bhikkhu Bodhi) says:

RIGHT LIVELIHOOD (1) Avoiding Wrong Livelihood “These five trades, O
  monks, should not be taken up by a lay follower: trading in weapons,
  trading in living beings, trading in meat, trading in intoxicants,
  trading in poison.” (AN 5: 177; III 208)

this is all that's said - beyond it is people's interpretations. This is my answer.
But if we want to go further, it may be of interest that the Buddha included cattle raising as an acceptable way to earn a living in AN 8.54 (also direct translation by Bhikkhu Bodhi):

“There are, Byagghapajja, four things that lead to the welfare and
  happiness of a family man in this very life. What four? The
  accomplishment of persistent effort, the accomplishment of protection,
  good friendship, and balanced living. “And what is the accomplishment
  of persistent effort? Here, Byagghapajja, whatever may be the means by
  which a family man earns his living— whether by farming, trade,
  cattle raising, archery or civil service, or by some other craft— he is skillful and diligent; he investigates the appropriate means,
  and is able to act and arrange everything properly. This is called the
  accomplishment of persistent effort.

One of the principal features of the Buddha’s teachings is that they were spoken to accord with the varying spiritual and mental needs and dispositions of the listeners.
As said in Essence of the Heart Sutra: The Dalai Lama's Heart of Wisdom Teachings

There is a verse in which Buddha urges his followers to take his words
  as they might accept from a jeweler a metal that appears to be gold:
  only after seeing that the metal does not tarnish when burned, can be
  easily cut, and can be polished to a bright shine should the metal be
  accepted as gold. Thus, the Buddha gives us his permission to
  critically examine even his own teachings. Buddha suggests we make a
  thorough inquiry into the truth of his words and verify them for
  ourselves, and only then “accept them, but not out of reverence.”

Another point to consider is the purpose of the teachings on Right View and Right Livelihood. As Bhikku Bodhi writes in his book The Noble Eightfold Path -

Though the principles laid down in this section restrain immoral
  actions and promote good conduct, their ultimate purpose is not so
  much ethical as spiritual. They are not prescribed merely as guides to
  action, but primarily as aids to mental purification.

and later quotes the Dhammapada:

To avoid all evil, to cultivate good, and to cleanse one's mind — this
  is the teaching of the Buddhas.

To this end, making a living destroying stuffed animals might be incompatible with your spiritual life, given the human tendency to anthropomorphize.
So my suggestion is to read the suttas and put them in context for the time, and apply them to the context of your life.

Pornography is also "meat" industry of "animals for slaughter". The Buddha said:

...the world would have fallen into promiscuity, as with goats, sheep, chickens, pigs, dogs and jackals. Lokapala Sutta
... corrupted too with prostitutes— that’s the way to disaster’s woe. Snp 1.6

Clearly animals suffer unjustly when they are used for human economic activities.
But it is also now a well-established fact that more than half of the greenhouse gases emitted by humans today are as a result of human’s desire for flesh, according to the UN, taking into account the entire process of raising, slaughtering, packaging, refrigerating and shipping animal flesh for consumption. So all humans are suffering also.
Even in the case where someone raises their own animals for slaughter, the animals suffer, though the secondary effect of contributing to human ecocide through climate disruption is lessened somewhat (less shipping, refrigeration, and packaging involved).
So is it ok to be a receptionist at a slaughterhouse, or a stock clerk in a supermarket selling animal flesh? Clearly no, but that doesn’t mean you are not abiding by the precepts—if you have no choice. We live within a corrupt and corrupting economic system that does not account for suffering, environmental destruction, nor climate destabilization.
What about a shoe salesman? Animal skin is often thought of as a waste product of butchering animals, but economically the value of the two products, flesh and skin, doesn’t justify considering either to be a waste product. So is it ok to sell leather shoes? Clearly not. But this question rarely comes up. Yet, in the case of both flesh and meat, the desire for them is unnecessary and ego-driven. How can any of you question the seriousness of any association with this industry?
From the Mahayana perspective (Surangama, Brahmajala, and Lankavatara sutras) the justification for the above points are clear. For example, from the Surangama:

The next important hindrance and allurement is the tendency of all sentient beings of all the six realms of existence to gratify their pride of egoism. To gain this one is prone to be unkind, to be unjust and cruel, to other sentient beings. This tendency lures them into the bondage of deaths and rebirth, but if this tendency can be controlled they will no longer be lured into this bondage for right control of mind will enable them to keep the Precept of kindness to all animate life. The reason for practicing dhyana and seeking to attain Samadhi is to escape from the suffering of life, but in seeking to escape from suffering ourselves, why should we inflict it upon others? Unless you can so control your minds that even the thought of brutal unkindness and killing is abhorrent, you will never be able to escape from the bondage of the world's life. No matter how keen you may be mentally, no matter how much you may be able to practice dhyana, no matter to how high a degree of Samadhi you may attain, unless you have wholly annihilated all tendency to unkindness toward others, you will ultimately fall into the realms of existence where the evil ghosts dwell.

There are three ranks of these ghosts: the highest are the mighty ghosts, the next are the Yaksha ghosts who fly in the air, and the lowest are the Raksha ghosts that live under the earth. Each of these ghosts has his double that disguises itself as having attained enlightenment. After my Parinirvana in the last kalpa these different kinds of ghosts will be encountered everywhere deceiving people and teaching them that they can eat meat and still attain enlightenment. But how can any faithful follower of the Lord Tathagata kill sentient life and eat the flesh?

You of this great assembly ought to appreciate that those human beings who might become enlightened and attain Samadhi, because of eating meat, can only hope to attain the rank of a great Raksha and until the end of their enjoyment of it must sink into the never ceasing round of deaths and rebirths. They are not true disciples of Buddha. If they kill sentient beings and eat the flesh, they will not be able to escape from this triple world. Therefore, Ananda, next to teaching the people of the last kalpa to put away all sexual lust, you must teach them to put an end to all killing and brutal cruelty.

If one is trying to practice dhyana and is still eating meat, he would be like a man closing his ears and shouting loudly and then asserting that he heard nothing. The more one conceals things, the more apparent they become. Pure and earnest bhikshus and Bodhisattva-Mahasattvas, when walking a narrow path, will never so much as tread on the growing grass beside the path. How can a bhikshu, who hopes to become a deliverer of others, himself be living on the flesh of other sentient beings?

Pure and earnest bhikshus, if they are true and sincere, will never wear clothing made of silk, nor wear boots made of leather because it involves the taking of life. Neither will they indulge in eating milk or cheese because thereby they are depriving the young animals of that which rightly belongs to them. It is only such true and sincere bhikshus who have repaid their karmic debts of previous lives, who will attain true emancipation, and who will no more be bound to wander to this triple world. To wear anything, or partake of anything for self-comfort, deceiving one's self as to the suffering it causes others or other sentient life, is to set up an affinity with that lower life which will draw them toward it. So all bhikshus must be very careful to live in all sincerity, refraining from even the appearance of unkindness to other life. It is such true hearted bhikshus who will attain a true emancipation. Even in one's speech and especially in one's teaching, one must practice kindness for no teaching that is unkind can be the true teaching of Buddha. Unkindness is the murderer of the life of Wisdom. This is the second admonition of the Lord Buddha as to the keeping of the Precepts.

Not OK because you are profiting from the bulk slaughter of animals (rather than using meat for occasionally personal nutriment).
OK because you are merely an employee rather than business owner.
OK because you are merely an employee rather than business owner.
OK because you are merely an employee rather than business owner.

What's the basis for this, how did you arrive at this answer? Are you distinguishing between employee and business owner? If a company offered me a job making weapons, or acting as a butcher, would that be OK because I'd be an employee not an owner? Conversely is anyone with mutual funds, index-linked or passive investments culpable, because they're shareholders of innumerable businesses?

Shareholder is a business owner, The teaching is about "wrong business". If the employee is slaughtering the animals, this is also wrong livelihood. But the question asks about a "cashier" or "general worker". The cashier is a cashier. The answers to these questions & answers are straightforward.

Right, the people who try to avoid all kinds of harm are called Jains, not Buddhists. It would be tough to find anything to do at all if we had to avoid any connection with harm at all.

"the people who try to avoid all kinds of harm are called Jains, not 'followers of the Buddha'" would that be also right @nocomprende ? ... very, very vage but possible also sadly right previous statement thinking on right resolve... and so (self) called Buddhists.


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Different interpretations of the 6 realms
What are the psychological and metaphorical interpretations of the 6 realms and why are they significant to some Buddhists but not others?

The psychological reality of the 6 realms is real & not metaphorical. Where as the  interpretations of the 6 realms as places that exist elsewhere, after the ending of life, is superstition. For example, when a vicious rapist or murderer or psychopath politician in the world is called "an animal", this is real & not a metaphor. They are animals & they are not human. In Buddhism, the word "human" ("manussa") means "high-minded" or "lofty-minded". The Pali suttas state a "human" lives in accordance with the Dhamma; with righteous conduct; without violence or exploitation ("devouring") of other beings. From the Buddhist point of view, not all people are "human". The book Buddha-Dhamma for Students may help here.
The real right understanding of the six realms is important to some Buddhists so they can see the world clearly (with dispassion), so they live the right way & so they can attain enlightenment. In other words, so they do not overestimate their spiritual progress & state. For example, many people who believe they are Buddhists & who are addicted to entertainment, sensuality, pornography, luxury, etc, believe the mind is "human" rather than the reality the mind is "hungry ghost". They believe by having superficial faith in the Buddha they will have a good reincarnation & don't realise the mind, in the here-&-now, is hungry ghost. This is how they overestimate their spiritual state.
Some Pali suttas listed below, which show the realms are mental states in the here-&-now.

I have seen, bhikkhus, the hell named ‘Contact’s Sixfold Base.’ There
  whatever form one sees with the eye is undesirable, never desirable;
  unlovely, never lovely; disagreeable, never agreeable. Whatever sound
  one hears with the ear … Whatever odour one smells with the nose …
  Whatever taste one savours with the tongue … Whatever tactile object
  one feels with the body … Whatever mental phenomenon one cognizes with
  the mind is undesirable, never desirable; unlovely, never lovely;
  disagreeable, never agreeable.
I have seen, bhikkhus, the heaven named ‘Contact’s Sixfold Base.’
  There whatever form one sees with the eye is desirable, never
  undesirable; lovely, never unlovely; agreeable, never disagreeable.
  Whatever sound one hears with the ear … Whatever odour one smells with
  the nose … Whatever taste one savours with the tongue … Whatever
  tactile object one feels with the body … Whatever mental phenomenon
  one cognizes with the mind is desirable, never undesirable; lovely,
  never unlovely; agreeable, never disagreeable.
SN 35.135

How has a monk attained/arrived at the state of a god?... A monk
  enters & dwells is the first...second...third...fourth jhana...
How has a monk attained/arrived at the state of a brahma?... A monk
  pervades the entire world with loving-kindness... compassion...
  appreciative joy... equinimity...
AN 4.190

Living with Brahma are those families where, within the home, mother
  and father are respected by their children. Living with the early
  devas (gods) are those families where, within the home, mother and
  father are respected by their children. For what reason? Because
  mother and father are very helpful to their children, they take care
  of them and bring them up and teach them about the world.
Mother and father are called "Brahma," "early teachers" And "worthy of
  veneration," Being compassionate towards Their family of children.
Iti 109

Bhikkhus, a god, a human or any other good state would not be evident
  from actions born of greed, hate and delusion. Yet, bhikkhus, from
  actions born of greed, hate and delusion a hellish being, an animal
  birth a ghostly birth or some other bad state would be evident.
AN 6.39

Bhikkhus, suppose a man would throw a yoke with a single hole into the
  great ocean, and there was a blind turtle which would come to the
  surface once every hundred years. What do you think, bhikkhus, would
  that blind turtle, coming to the surface once every hundred years,
  insert its neck into that yoke with a single hole?
If it would ever do so, venerable sir, it would be only after a very
  long time.
Sooner, I say, would that blind turtle, coming to the surface once
  every hundred years, insert its neck into that yoke with a single hole
  than the fool who has gone once to the nether world would regain the
  human state. For what reason? Because here, bhikkhus, there is no
  conduct guided by the Dhamma, no righteous conduct, no wholesome
  activity, no meritorious activity. Here there prevails mutual
  devouring, the devouring of the weak. For what reason? Because,
  bhikkhus, they have not seen the Four Noble Truths. What four? The
  noble truth of suffering … the noble truth of the way leading to the
  cessation of suffering.
SN 56.47

Now on that occasion the wanderers of other persuasions had come
  together in a gathering and were sitting, discussing many kinds of
  bestial (animal) topics, making a great noise and racket. AN 10.93

Bhikkhus, these two bright principles protect the world. What are the
  two? Shame and fear of wrongdoing. If, bhikkhus, these two bright
  principles did not protect the world, there would not be discerned
  respect for mother or maternal aunt or maternal uncle’s wife or a
  teacher’s wife or the wives of other honored persons, and the world
  would have fallen into promiscuity, as with goats, sheep, chickens,
  pigs, dogs, and jackals. But as these two bright principles protect
  the world, there is discerned respect for mother… and the wives of
  other honored persons. AN 2.9

Beings (sattā) are few who, when they pass away from the animal realm
  (tiracchānayoniyā) are 'reborn' (paccājāyanti) among humans
  (manussesu)… those beings are more numerous are reborn in hell…. For
  what reason? They have not realised the Four Noble Truths. SN 56.102
  to 131

Householders, there are these four ways of living together. What four?
A wretch lives together with a wretch; a wretch lives together with a
  female deva (god); a deva (god) lives together with a wretch; a deva
  (god) lives together with a female deva (god).
When both are immoral, miserly and abusive, husband and wife live
  together as wretches.
The husband is immoral, miserly and abusive, but his wife is virtuous,
  charitable, generous. She is a female deva living with a wretched
  husband.
The husband is virtuous, charitable, generous, but his wife is
  immoral, miserly and abusive. She is a wretch living with a deva
  husband.
Both husband and wife are endowed with faith, charitable and
  self-controlled, living their lives righteously, addressing each other
  with pleasant words.
Then many benefits accrue to them and they dwell at ease. Their
  enemies are saddened when both are the same in virtue.
Having practiced the Dhamma here, the same in virtuous behavior and
  observances, delighting in a deva world, they rejoice, enjoying
  sensual pleasures.
AN 4.53

And what is the origination of the world? Dependent on the eye & forms
  there arises eye-consciousness. The meeting of the three is contact.
  From contact as a requisite condition comes feeling. From feeling as a
  requisite condition comes craving. From craving as a requisite
  condition comes clinging. From clinging as a requisite condition comes
  becoming. From becoming as a requisite condition comes birth. From
  birth as a requisite condition, then aging & death, sorrow,
  lamentation, pain, distress, & despair come into play. This is the
  origination of the world. SN 12.44

Here, Udayi, the bhikkhu secluded from sensual desires and thoughts of
  demerit abides in the first jhana: Overcoming thoughts and thought
  processes and the mind in one point internally appeased, without
  thoughts and thought processes abides in the second jhana. Again with
  equanimity to joy and detachment, feeling pleasant with the body too,
  abides in the third jhana. To this the noble ones say abiding in
  pleasantness with equanimity. Udayi, this is the course of actions,
  for realising the world of only pleasant feelings (ekantasukhassa
  lokassa). MN 79

Sensual desire… ill-will (anger)… sloth & drowsiness… restlessness &
  anxiety… uncertainty is an obstacle, a hindrance that overwhelms the
  mind and weakens wisdom… when a monk has not abandoned these five
  obstacles… for him to understand what is for his own benefit, to
  understand what is for the benefit of others, to understand what is
  for the benefit of both, to realize a superior human (manussa) state
  (dhammā), a truly noble distinction in knowledge & vision: that is
  impossible. AN 5.51

So the realms can be used to describe both mental states and personalities of individuals?

Minds can move or shift ("cuti') between different realms however there certainly can be individuals with a strong predominant conditioning in one realm.

The gross psychological interpretations of the 6 realms are as follows: hate (hells), craving (pretas), stupidity (animals), passion (people), belligerance (asuras) and pride (gods, or devas). These are samsaric worlds, which means that even the worlds of gods are still mundane, not 'spiritual'.
That means that it is important to understand 'a realm level' for mundane purposes or for understanding another person's / one's own state of mind/existance, that is, at least from the first two Noble Truths, but it's irrelevant from the point of the Fourth Noble Truth (ayam dukkha-nirodha-gamini patipada).
There are also four more realms in the Tiantai school and  Nichiren lineage that give a way to liberation from the samsaric existance, which makes ten worlds altogether.
These are of Learning, Realisation, Boddhisattvas and Buddhahood. As milestones on a path, they are important from the position of the Third and Fourth Noble Truths.
In Nichiren lineage, this interpretation results in ichinen-sanzen concept stating that any moment of a human consciousness embraces three thousand different states of mind from the ten worlds.
Because a human being can hardly encompass all the three thousand states at a time, it is not important from an [unadvanced] layman's perspective, since in terms of conventional logic we are capable of perceiving only a single state of mind within a given moment.

Six realms are mental states those experience even by humans. E.g Human being act like animals(only behave as responds to instincts) You are correct;  realms can be used to describe both mental states and personalities of individuals.
See my interpretation and examples in this topic: My explanation of six realms of existence
And be note that six realms can't be divided by standard line. The characteristics are mixed gradually with other  realms.That's why it is so difficult to analyze individual. But when human society is examined carefully behavior of six realms can be seen clearly.

To answer the question of "why are they significant to some Buddhists but not others?", I would say that some Buddhists are not interested in the psychological and metaphorical interpretations of the six realms, because they take the six realms to be real places that beings are reborn into.
And why do these Buddhists assume the six realms are literally existent places? They assume so because the Buddha said so.
In the Janussonin Sutta, Janussonin asks the Buddha whether deceased relatives would receive the gifts (I guess food) offered to them? The Buddha says that deceased relatives would not receive the gifts offered to them, if they were reborn in non-hungry-shade realms.
To quote an example:

"There is the case, brahman, where a certain person takes life, takes
  what is not given, engages in sensual misconduct, engages in false
  speech, engages in divisive speech, engages in abusive speech, engages
  in idle chatter, is covetous, bears ill will, and has wrong views.
  With the break-up of the body, after death, he reappears in hell. He
  lives there, he remains there, by means of whatever is the food of
  hell-beings. This is an impossible place for that gift to accrue to
  one staying there.

Above, it clearly says, "with the break-up of the body, after death, he reappears in ...". This is very unequivocal that someone's body breaks up and then he is reborn somewhere else in another realm.
As for hungry shades or hungry ghosts (peta):

"Then there is the case where a certain person takes life, takes what
  is not given, engages in sensual misconduct, engages in false speech,
  engages in divisive speech, engages in abusive speech, engages in idle
  chatter, is covetous, bears ill will, and has wrong views. With the
  break-up of the body, after death, he reappears in the realms of the
  hungry shades. He lives there, he remains there, by means of whatever
  is the food of hungry shades. He lives there, he remains that, by
  means of whatever his friends or relatives give in dedication to him.
  This is the possible place for that gift to accrue to one staying
  there.

Ven. Narada Mahathera wrote here:

Peta-yoni (pa + ita) lit., departed beings, or those absolutely devoid
  of happiness. They are not disembodied spirits of ghosts. They possess
  deformed physical forms of varying magnitude, generally invisible to
  the naked eye. They have no planes of their own, but live in forests,
  dirty surroundings, etc.

My personal hypothesis is that hungry shades are actually microbes in the environment. Hence, they are able to literally consume food offered to the deceased.

This seems very clear now, but if the Buddha said the realms are real places then why do some regard other interpretations as being important?

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text:
Meditation - how to breathe naturally?
Just starting with meditation, I can't get the breathing right.
As soon as I concentrate on breathing (as there is not much else to concentrate on), I unvolunteraly assume concious control over when to breath in and out.
That leads to either to little or to much breathing and makes me feel dizzy.
How ever, when I stop conciously breathing in and out, I don't breath at all - my breathing reflex wont kick in as long as I think about breathing. The result is an awkward cycle of holding breath, turning blue, conciously breathing like just surfaced from a freedive, holding breath again.
Not thinking about breathing works only so long before I realise that I avoid to think about breathing...
Is this common at all? How do you handle this?

See also Hard not to control my breathing

I bicycle regularly so maybe I'm good at breathing (get a good amount of oxygen from each breath).
If I sit at rest I seem to need about 4 breaths per minutes. Apparently that's abnormal (maybe even pathological), the internet says that 12/minute is normal for adults, 8/minute for athletes. Also I've been diagnosed with sleep apnea so I have a CPAP machine for sleeping. I say this to warn you that "your mileage may vary".
Anyway, sitting at rest it takes me about:

5 seconds to inhale
5 seconds to exhale
Pause for about 5 seconds, until my body feels it wants to begin to take another breath to avoid a shortage

So 15 seconds per cycle, 4 per minute, including a 5 second pause in each cycle.
I breathe continuously on a bicycle (i.e. during aerobic exercise), and don't try to breathe continuously when I'm at rest, i.e. at rest I do expect to pause between each breath -- and not take the next breath until I feel I begin to need it.
It doesn't have to be exact: if you start a breath a couple of seconds too late or too early, it doesn't matter.
By breathing deeply and continuously I can slow that to 3 breaths/minute:

10 seconds to inhale
10 seconds to exhale
No pause between breaths

That feels abnormal though, an effort to breathe extra deeply and extra slowly.
Anyway, maybe what you're missing is the pause between breaths. IMO if I didn't pause (when I'm at rest) I'd hyperventilate. You can vary the duration of the pause. The trick is not to begin to inhale, until you begin to feel that you begin to need the next breath. If you wait until you just begin to need to breath, don't worry: because you're at rest you'll easily be able to satisfy your need with just one breath, maybe two at most.
Sometimes there's a sudden urge to take an extra quick inhale. If that happens then just let that happen.
Also you wrote, "an awkward cycle of holding breath", as if you're pausing with your lungs full. I pause after each exhale:

Inhale engages some muscular effort
Exhale releases that muscular effort
Pause/idle while the muscles are at rest (not breathing and the body held upright just by being balanced on an upright skeleton, minimum use of muscles to hold yourself in place).

See also How to breathe into your stomach and not get light headed during meditation?
I kind of recommend the book, Anapanasati -- Unveiling the Secrets of Life by Bikkhu Buddhadasa ... plenty of detail, adapt as necessary.

When I started meditation it was also a major problem for me.
Just as you described, when you are unconsiously controlling your breath while trying not to, you either breath too much or too little. The sensation is really unpleasant as, in addiation to the bad breathing, it feels like you are not doing the meditation right.
This is a good thing to realize, because you will know that you are controlling your breath as soon as these symptoms arise.
So one of the reaction you may have is  trying to force not controlling your breath, and to make all kind of mental effort. This is not a good solution, because it will create tension and hinder your concentration even more.
What tend to work for me is the exact opposite reaction: just relax, take a step back
Think that this meditation is a skill that needs a lot of time and practice, and that you are not supposed to do everything perfectely when you are beginning.
Maybe take a little break from the breathing, switch your object of concentration to the sounds in the room, or the sensation in your feets, while your breath naturaly comes back to it's own pace. Then, rather than trying on the breath as one single entity, you may try to break it down in several parts: experience what sensations arise on the inspiration, the expiration, what you feel in your nose, in the abdomen, what is the quality of air in the room, it is warm, cold, etc.
Rather than focusing on controlling or not controlling the breath, or trying to experience the pace of the flow of air, which can be very challenging at first, you might try to focus on other sensation that involve the breath, like those that I described above, which I believe are easier to meditate on at this stage.
As you progress, you will find it easier not to controll the breath, remember that it is a skill that you do not need to master right now. It is really easy to make wrong jugement about yourself because you feel like you are not progressing quickly enough, or because you feel like your meditation session is not working as intented.
I think what really matters at first, is sitting through all of this, no matter what happens. The key is to relax and let the problems arise, notice them and let them disappear by themselves. No forcing, no jugement.
Good luck :)

Even trying not to control  is a form of control. Trying not to control the breath is just further control of the breath.
The best thing to do is to just accept the breath as it is even when it seems we are controlling it. Our beginning mindful dealings with the breath often come with this confusion about trying not to control our own breath. When I accepted the breath and any control I might be exerting over it, there seemed to be no longer any problem with controlling my breath anymore. I just observed  the breath in whatever state it was in and the perceived problem went away.
Here is a video of Bhante Yuttadhammo explaining this better than me:
https://youtu.be/HkgWBDwUtIM
P0

Let me first assure you that nothing bad is going to happen if you allow yourself to stop breathing.  Your reptilian brain is eventually going to demand breath and you will have no choice but to inhale.  What you are experiencing is actually a very good sign and one that indicates that you are moving very close to what we in Zen would call shunyata or Mu.  The trick here is to not get swept up in the feelings of agitation and frustration that these breath stoppage are causing you.  Instead, sink into the blank spaces of non-breathing.  Have complete faith in your body's ability to take care of its own breathing without your willful intervention.  Relax.
As you do this, those first couple of inhalations may come deeply and sharply.  That's ok.  Let your body take what air it wants.  As you keep relaxing and relinquishing control, you will start to notice those breaths become softer and more subtle.  You exhalations will start to slow down.  Eventually, you will reach a state where the breath is long, slow, and deep like a person sleeping.  This is where you want to be.  Trust in your body's ability to find its own way there.

Forget about breathing in and out and just focus on the sensation that arises and falls when the air hits the nose. If wanting to control arises, note it as wanting... wanting... wanting... until it goes away and get back to noting the sensation at the nose. If worry arises that you are controlling, note it as worrying... worrying... worrying... until it disappears and get back to noting the sensation at the nose.
Do not assume things like 'I','me' or 'mine' when there are only 6 senses and none of them can sense 'I', "I am", 'me' or 'mine'. They can only sense sense-objects.

+1, though maybe at this stage of the game, it might be better to watch the rise and fall of the abdomen.  The nose might be a little too subtle at this point.

Abdomen or nose, just stick to one place.

Thanks! Please not that I don't have an "urge" to control breathing, it's simply that as soon as I think about breathing I stop to breathing automatically.

Welcome! Meditate on the thinking as thinking... thinking... thinking... or worrying... worrying... worrying...

recommend to see my answer in https://buddhism.stackexchange.com/a/24514/10100
For disappearing breath  issue, the practitioner is facing to...

Fear of death because of the disappearing breath.
Doubt wheather "how to manage  disappearing breath situation" because the practitioner may be misunderstanding wheather "I am not breathing" although the fact is  the practitioner still breathing but his concentration is not strong enough, weak, to find the breath.

So, the practitioner should resolves those issues by realizing that he is not the excepted person who can be alive without breath. By this way, the practitioner  will leave those issues and be back to concentrate on the tip of the nose and wait for the appearing of the breath without fear, worry and doubt issues. See the path of purification]1 page 276:

These are the means for doing it. The bhikkhu should recognize the unmanifest state of the meditation subject and consider thus:
  “Where do these in-breaths and out-breaths exist? Where do they not?
  In whom do they exist? In whom not?” Then, as he considers thus, he
  finds that they do not exist in one inside the mother’s womb, or in
  those drowned in water, or likewise in unconscious beings,58 or in the
  dead, or in those attained to the fourth jhána, or in those born into
  a fine-material or immaterial existence, or in those attained to
  cessation [of perception and feeling]. So he should apostrophize
  himself thus: “You with all your wisdom are certainly not inside a
  mother’s womb or drowned in water or in the unconscious existence or
  dead or attained to the fourth jhána or born into the fine-material or
  immaterial existence or attained to cessation. Those in-breaths and
  out-breath are actually existent in you, only you are not able to
  discern them because your understanding is dull.” Then, fixing his
  mind on the place normally touched [by the breaths], he should proceed
  to give his attention to that.

You are learning that breath is unstable, mind is unstable, you cant just look at the breath. There is a lesson here.

One should not resort to controlled or forced breathing as this practice is Pranayama one of the contemporary practices the Buddha tried and rejected in favour of Anapanasati as described in Ariyapariyesana Sutta, Mahā Sīha,nāda Sutta, Maha Saccaka Sutta.
In Anapanasati one just watchers the breath passively with no voluntary alterations.

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text:
The mind experiment of rebirh
Assume that the earth destroyed just a fraction of second as a result of massive meteoroid collision and there are only 10000 humans live at the moment. A one human being possess strong qualifications to get the rebirth as human again.(karmic effects,exact "chuthi citta" at the moment of death and etc....). So what happen next as there are no conditions to get the rebirth as human again?

Human realm is not the only realm of existence. There are 31 in total. Also, it doesn't say that earth is the only place in the universe where humans live. So the person could be born in another human realm or the closest thing to it.
In any case, it's a purely hypothetical situation. I doubt that a meteoroid can destroy the earth in fraction of a second. Someone will probably have to instantly place the earth on the sun or in a black hole for such a thing to  happen.

Answer is superficial and based on assumptions as you mention the earth is the only place in the universe where humans live.

The question is superficial and based on many assumptions and I did not say that earth is the only place where humans live. Read again.

sorry. yes you have mention there are other places in universe where human lives. So what are those planets in universe?

sorry. yes you have mention there are other places in universe where  human lives. So what are those planets in universe?  it's a purely hypothetical situation- yes that's why I have mention this is a mind experiment. Also you are confirming existence of life in universe except of earth as mention in scriptures. My aim of question is how do you implement  or apply rebirth.

My meteoroid example is just to describe that existence of humans and other form of life forms completely wiped out from earth.( similar to extinction of dinosaurs.)

Earth is getting destroyed at the end of every Kalpa and it is reformed. Still the humans move on. Read the Sapta Suriya Sutta and the Agganna Sutta.

In A.N. Tikanipāta Cūḷanīsutta:

Cūlanikāsuttaṃ –– The thousandfold world system

Venerable Ānanda approached the Blessed One, worshipped, sat on a side and said to the Blessed One: Venerable sir, these words I heard
  from the Blessed One and are acknowledged by the Blessed One: Ānanda,
  Abhibhū, a disciple of the Blessed One Siki makes announcements to the
  thousandfold world systems at one and same time from the world of
  Brahma. Venerable sir, the Blessed One worthy and rightfully
  enlightened, making an announcement how far could you be heard?
Ānanda, he is a disciple of an immeasurable number of Thus Gone Ones.
For the second time venerable Ānanda said: Venerable sir, these words
  I heard from the Blessed One and are acknowledged by the Blessed One:
  Ānanda, Abhibhū, a disciple of the Blessed One Siki makes
  announcements to the thousandfold world systems at one and same time
  from the world of Brahma. Venerable sir, the Blessed One worthy and
  rightfully enlightened, making an announcement how far could you be
  heard?
Ānanda, he is a disciple of an immeasurable number of Thus Gone Ones.
For the third time venerable Ānanda said : Venerable sir, these words
  I heard from the Blessed One and are acknowledged by the Blessed One:
  Ānanda, Abhibhū, a disciple of the Blessed One Siki makes
  announcements to the thousandfold world systems at one and same time
  from the world of Brahma. Venerable sir, the Blessed One worthy and
  rightfully enlightened, making an announcement how far could you be
  heard?
Ānanda, have you heard of the Cūlanika thousandfold world system?
Venerable sir, Blessed One, Well Gone One, now is the time to hear it.
  The bhikkhus hearing it from the Blessed One will bear it .
Then Ānanda, listen and attend carefully, I will tell.
The Blessed One said: Ānanda, as long as the moon and sun illuminate
  the directions, till then the thousandfold world systems will prevail,
  with a thousand, moons, suns, Mahameru mountains, Indian peninsulars,
  Aparagoyanas, Uttarakurus, Pubhavidehas, fourfold oceans, fourfold
  rulers, fourfold guardian kings, heavens of the thirty-three, heavens
  of Titan gods, heavens of happiness, heavens of the gods of creation,
  heavens of the gods who create others, worlds of Brahma. Ānanda, to
  this is called the thousandfold Cūlanika world system. Ānanda, as long
  as the thousandfold Cūlanika world system prevails till then the
  thousandfold world system, calls this the two thousandfold middle
  world system. Ānanda, as long as the two thousandfold middle world
  element prevails till then the thousandfold world system calls this
  the three thousandfold and the great thousandfold world system.
  Ānanda, if the Thus Gone One desires, he announces to the three
  thousandfold and the great thousandfold world system.
Venerable sir, how does the Blessed One, if he desires announce to the
  three thousandfold and the great thousandfold world system?
Here Ānanda, the Thus Gone One pervades the three thousandfold and the
  great thousandfold world system with an effulgent light, so that those
  sentient beings see it, then the Thus Gone One makes a sound. In this
  manner an announcement is made to the three thousandfold and the great
  thousandfold world system if he desires.
When this was said venerable Ānanda said to venerable Udayi: It is
  great gain for me that my Teacher is so powerful.
When this was said venerable Udayi said: Friend Ānanda, what does it
  matter to you, when your Teacher is so powerful?
Udayi, do not say so. If Ānanda passes away without freeing his mind
  from greed, on account of that pleasant mind, he will be ruler of gods
  for a hundred times. In this same peninsular of India he will be the
  ruler. Yet Udayi Ānanda will extinguish in this same life.


text:
kamma wise why cant i do a steady practice
I have ups and downs in my practice  (time doing formal mediation - time being mindful in daily life - doing good stuff avoiding bad stuff etc)
and also ups and downs in completely mundane issues as well  being lazy not doing anything for days to do stuff for my own benefit than doing lots of stuff (washing the house - exercise etc)  than back to nothing  )
I had times in the past where i mediated every day (in retreat but also at home)  and times i did stuff like exercise study stuff etc
now im in a slump for a few months doing almost nothing  -  i wonder how is it explained kamma wise  ....  bad kamma from the past  ?  lazy kamma ?  is there no way to prevent this ?
again asking from a kamma point of view  -  how to make a steady practice  and steady good mundane stuff can be great (do i need some tipping point of good vs bad kamma done in this specific lifetime)  but more than that WHY it happens
also  : how effective is current life kamma compared to past live kamma ?  and recent kamma (1-3 months) in comparison to kamma made before (3months -99 years)

Firstly, if you keep wallowing in self-pity over your assumed past kamma, then this will not help you move forward. It's considered unwholesome. So, forget about it. Similar to the Buddha's Parable of the Poisoned Arrow, you should think about how you can get the arrow out and heal yourself, rather than examining the origins of the arrow.
Secondly, it sounds like you are afflicted with one of The Five Hindrances called Sloth and Torpor.
Here's some advice by Ajahn Brahm on this:

Sloth and torpor is overcome by rousing energy. Energy is always
  available but few know how to turn on the switch, as it were. Setting
  a goal, a reasonable goal, is a wise and effective way to generate
  energy, as is deliberately developing interest in the task at hand. A
  young child has a natural interest, and consequent energy, because its
  world is so new. Thus, if one can learn to look at one's life, or
  one's meditation, with a 'beginner's mind' one can see ever new angles
  and fresh possibilities which keep one distant from sloth and torpor,
  alive and energetic. Similarly, one can develop delight in whatever
  one is doing by training one's perception to see the beautiful in the
  ordinary, thereby generating the interest which avoids the half-death
  that is sloth and torpor.

More advice by Gil Fronsdal here. I quote some parts of it below:

The presence of sloth and torpor does not mean that energy is not
  available. It means we are not accessing it. With a change in
  conditions, energy may reappear in a moment. This can be seen clearly
  in young children who switch from being “tired” (while shopping, for
  instance) to being energetic (about an offer of ice cream, for
  instance) in a matter of seconds. The energy level depends on whether
  they evaluate the situation as boring or exciting.
Chronic sloth and torpor may represent a lack of meaning or purpose in
  life. In this case, the antidote might involve taking time for deep
  inner reflection or thoughtful conversations with wise friends.
When sloth and torpor are present and energy is weak, we do the best
  we can. When they are absent, energy will naturally be stronger.
  Rather than berating yourself when you are tired or praising yourself
  when you are alert, just keep practicing. Certainly it will help
  reveal the precious beauty of your own mind.

In case of porpuse i have a purpose to advance in the path  - but since i never manage to get a persistent practice no matter what i try  its hard to get motivation  -  trying no formal meditation trying retreats doing meditation all day trying 1 minute meditation a day etc   -    all dont seem to help and i get to periods of 3-5 months without any meditation and little mindfulness after this tries fail

I suppose practice is a kind of methodical karma.

If practice seems  wonderful all the time and feels great, it might be that something is wrong with the practice.

On the other hand...

Practice can seem to unfold in an erratic way that might involve the following issues:
-a distracted practice or no practice at all engulfed by defiled distractions that might happen for days before a more focused practice arises for some time only to cycle back to a more distracted practice again. This might happen over and over changing as we learn and unlearn good habits and bad habits. Our habits are the engine of our karma.
-vaguely feeling like something is missing.
-feeling like it should be an easy thing to control the practice but somehow it isn't.
-experiencing a lot of tension and stress and usually not knowing exactly why.
-seeing that things just keep cycling around and around.
If practice contains any of the above then chances are  you are practicing better than you might think.

(I should note that the  above advice is for people who are practicing some kind of vipassana mindfulness outside an intensive retreat. It's not intended for a samatha or concentration practice)
I always wondered why we don't go into greater detail about how we  practice in this forum. This greater detail would give a bit of an indication of your karma at least for others to give you their advice about it.
Maybe your karma doesn't have enough encouragement behind it.
I found myself needing advice on how to get myself practicing. I found many useful and free dana ebooks written by various teachers online. Also, I found books on how to stop procrastination very helpful(there are a lot out there just for free on the internet!)
Here is just one book I found useful and I hope you would too. It's easy to read and gets right to the point (IMHO) by Bhante Bodhidhamma entitled ENCOURAGEMENTS TOWARDS AWAKENING:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.satipanya.org.uk/wp-content/uploads/2015/09/ENCOURAGEMENTS.pdf&ved=0ahUKEwjIprGCoLzYAhUqllQKHehgA_0QFgglMAA&usg=AOvVaw1tTdpJOL6sHHSaN4L-GAH7
If so desired, I can give out more titles by obscure but wise teachers that might not be so well known by practitioners here. I like reading all these teachers because they each come at the practice and the Dharma from many different unique angles.
I hope you find good answers to what your looking for and you keep on practicing :) -Metta

thanks - from where is the second quote ?

I'm sorry, I'm not totally sure what part you mean. What are the first 3 words of the quote?

"Practice can seem"

It sounds to me that you are just looking for a scriptural justification for not practicing.  What I think you want is some answer that make it seem OK that you are unwilling to muster the effort required for practice.  Right now, work on cutting off that karmic path.  You can start that process by sitting everyday.  Begin with one second.  Add a second each day.  It may not seem like much, but it is more than you are doing now.  It will also help get your karma moving in the right direction.

Koan 17 of the Hekiganroku
  Introduction
Cutting through nails and breaking steel for the first time, one could
  be called a Master of the First Principle. If you run away from arrows
  and evade swords you will be a failure in Zen. The place where even a
  needle cannot enter I’ll leave aside for a while, but when the foaming
  billows wash the sky, what will you do with yourself then?
Case
A monk asked Kyorin, “What is the meaning of Bodhidharma’s coming from
  the west?” “Sitting long and getting tired.”

The only karma that has any true bearing on your practice are the actions you engage in now.  Pondering your own karmic roots - roots that suttas tell us are only knowable to a Buddha - is futile, but even knowing them will have no impact.  Intellectualism like this is nothing more than a strategy to avoid the arrows and swords of practice.

you are wrong about the first part - about the one second technique - tried that many times and didnt work usually lasts 2  days  sometimes it did last and build to 2 hours a day but breaks shortly after that time -  even attempts at doing just 5 minutes a day without adding time fail  and after each try like that comes a few months of nothing - that is why im more trying to understand the why  than the how  - how it works exactly kamma wise    "but more than that WHY it happens "

in the original intetion i didnt even to plan to asy about my personal practice but on kamma but couldnt think o f a way to write this question

It happens because you aren't exerting effort; the same would apply in a more general sense.

but i do exert effort sometimes a lot of effort like the retreats i did doing 2 hour mediation  all day

About the latest edit :  i am not asking about my specific  karma  - but karma in general  -- which is  a big difference

It's not different.  In both cases, karma is unknowable and not something to be fretted over.  Only your current actions are fully in your control.  Regarding effort, it's not a "sometimes" thing.  It's to be undertaken all the time.  Keep your practice so close that no air can escape.

You shouldnt speculate about your own kamma  thats true but talk about kamma in genral is fine  -  im asking about the way kamma works -  a thing which is talked about by many monks

I just told you how it works.  :-P  Act now, reap the fruit later.  All that matters is now.

Im asking about a specific thing about how kamma works not in general  - i can use google for that

This is the last I'm going to say on the subject - "how to make a steady practice and steady good mundane stuff can be great" - by exerting effort now.  Karma is best understood as a kind of moral momentum.  Every time the wheel comes by, you push it again.  That push is what matters.  "how effective is current life kamma compared to past live kamma ? [etc.]"  None of these are as important as "now" karma.


text:
What does the first para of Lonaphala Sutta mean?
The first paragraph of the Lonaphala Sutta, translated by Thanissaro Bhikkhu, states:

"Monks, for anyone who says, 'In whatever way a person makes kamma,
  that is how it is experienced,' there is no living of the holy life,
  there is no opportunity for the right ending of stress. But for anyone
  who says, 'When a person makes kamma to be felt in such & such a way,
  that is how its result is experienced,' there is the living of the
  holy life, there is the opportunity for the right ending of stress.

I feel that this is not the best possible translation for this paragraph of the sutta.
Please explain what it really means.

This is how I understand it.  You don't get back exactly what you put in, but you get back the results of it.
Example,  if you kill someone, it is not necessary that you will get killed back in return but you will get results from your killing which depends on many factors.  This sutta,  Buddha taught us that is possible to work on those many factors that could produce a better results.
Like , if I killed someone, then later worked to become a stream enter, a result that could have sent me to hell next life changed to make me a sickly person.  Etc. A Finger bandit arahat is another example.
It is clear to me that karma is not fate or fixed destinations or replacement of a will from a god.

I scored you answer down because to me the answer is not related to the theme or context of the sutta. –

I believe this is the correct answer. Basically the sutta is a caution against popular interpretations of karma. It’s not like if you drop a ping pong ball on someone, that someone else is going to drop a ping pong ball on you too, and then some other person is going to go: “ha, karma is an XYZ!” Rather a person creates karma and then its result is experienced in such and such a way dependent on other factors.

Translation:

Bhikkhus, if someone says:  "how many actions a person done are how many
  results a person get back". Bhikkhus, if that be so, there is no
  meditation for enlightenment and there is no apparent path to end
  suffering rightfully.
Bhikkhus, if a person says: "how many actions a person done, only results
  which possible to get back, are how many results a person get back".
  Bhikkhus, if that be so, there is no meditation for enlightenment and
  there is no apparent path to end suffering rightfully.
http://www.84000.org/tipitaka/read/v.php?B=20&A=6567&Z=6647&eng=metta_e
(I modified from that link.)

Why I translate like that?
I combine above titles with their explanation below. Because in ancient theravāda study system culture, sutta's context must relate each others. This is called tanti-bhāsā.

Here bhikkhus, a certain person doing a trifling evil action would pull him to hell. Here bhikkhus, a certain person doing a trifling evil action of the same nature would feel it here and now and mostly nothing would be apparent.
Bhikkhus, what kind of person doing a trifling evil action, on account of it, be pulled to hell?.
Here bhikkhus, a certain person is undeveloped, in body,2 virtues,2 in mind,[3] in wisdom,[4] is insignificant with a small self[5] living in unpleasantness. Bhikkhus, such a person doing a trifling evil action would pull him to hell (uppapajja-vedanīya;  this life's and hell in next life's results of puthujana are possible to get back).
Bhikkhus, what kind of person doing a trifling evil action of the same nature would feel it here and now and mostly nothing would be apparent?
Here bhikkhus, a certain person (ariya) is developed, in body, virtues, in mind, in wisdom, is with a significant self immeasureable and living in pleasantness. Bhikkhus, such a person doing a trifling evil action of the same nature would feel it here and now (diṭṭhadhamma-vedanīya; this life's results of ariya are possible, but hell in next life is impossible) and mostly nothing would be apparent.

So, "how many actions, ditthadhamma-vedanīya and hell in upapajja-vedanīya, a person done, only results which possible to get back, are how many results a person get back". (puthujana can get both diṭṭhadhamma-vedanīya and hell in upapajja-vedanīya back, but ariya can get just diṭṭhadhamma-vedanīya back.)
Therefore buddha taught in Cakkhu Sutta:

“Monks, if anyone takes faith and is settled in these things (be sotāpanna-ariya), it is said he lives in conformity with faith, has entered the righteous way, the way of Great Beings, has gone beyond the field of ordinary man, and it is not possible that he is doing actions that lead to hell, the animal womb, or the sphere of ghosts be born there. It is not possible that he should die without realizing the fruits of entry in the stream of the Teaching.

While I am not fluent in the exact translation, the translation offered is as follows:

Monks, for anyone who says, 'In whatever way a person makes kamma, that is how it is experienced,' there is no living of the holy life,
  there is no opportunity for the right ending of stress. But for anyone
  who says, 'When a person makes kamma to be felt in such & such a way,
  that is how its result is experienced,' there is the living of the
  holy life, there is the opportunity for the right ending of stress.
There is the case where a trifling evil deed done by a certain individual takes him to hell. There is the case where the very same
  sort of trifling deed done by another individual is experienced in the
  here & now, and for the most part barely appears for a moment.

Based on reading the above two paragraphs, it appears the meaning of the sutta is:

When the Holy Life has been lived, an act of evil kamma, performed due a lapse of mindfulness, does not necessarily bring an evil result, i.e. a result of suffering (which can only occur due to egoistic attachment or self-view).
When the Holy Life has been lived, where there is skill in mindfulness &  wisdom, an act of evil kamma, performed due a lapse of mindfulness, only brings the result of vedana (feeling). Where a certain individual is developed in [contemplating] the body, developed in virtue, developed in mind, developed in discernment: unrestricted, large-hearted, dwelling with the immeasurable, the following occurs in relation to an act of evil kamma, in the here-&-now:

On cognizing a mind-object with the mind, he does not lust after it if it is pleasing; he does not dislike it if it is unpleasing.  He abides with mindfulness of the body established, with an immeasurable mind, and he understands as it actually is the deliverance of mind and deliverance by wisdom wherein those evil unwholesome states cease without remainder. Having thus abandoned favouring and opposing, whatever feeling he feels, whether pleasant or painful or neither-painful-nor-pleasant, he does not delight in that feeling, welcome it, or remain holding to it. As he does not do so, delight in feelings ceases in him. With the
  cessation of his delight comes cessation of clinging; with the
  cessation of clinging, cessation of being; with the cessation of
  being, cessation of birth; with the cessation of birth, ageing and
  death, sorrow, lamentation, pain, grief, and despair cease. Such is
  the cessation of this whole mass of suffering.
MN 38

As was taught in AN 3.61:

Now it is for one who feels that I proclaim: ‘This is suffering,’ and ‘This is the origin of suffering,’ and ‘This is the cessation of
  suffering,’ and ‘This is the way leading to the cessation of
  suffering.’


text:
How do we guarantee the accuracy and validity of Buddhist scriptures?
In this site participators draw statements from "Buddhist scriptures" (Suttas), considering them pure and directly from Buddha's words.
Some of these statements [seem] closer to fantasy, supernaturals, assumptions and speculations; and few are false statements (e.g "thoughts are generated in heart" is mentioned in Abhidharma). Also information extracted from Buddhist scriptures are mixed with Hindu concepts as milk and water (most of original Buddhist scriptures were destroyed in Thakshila). In the kalama sutta it mentions that to completely depend on scriptures is useless.
So how it can be verified statements exactly from Buddha himself (not as a label or maintain faith) just to get progress of right learning and confidence? Buddhism has history of 2500 years, and scriptures were produced around 300 years after death of Buddha. So how do we guarantee the accuracy and validity of thousands of Buddhist scriptures?

Here's another example:

Then Ānanda, listen and attend carefully, I will tell.
The Blessed One said: Ānanda, as long as the moon and sun illuminate the directions, till then the thousandfold world systems will prevail, with a thousand, moons, suns, Mahameru mountains, Indian peninsulars, Aparagoyanas, Uttarakurus, Pubhavidehas, fourfold oceans, fourfold rulers, fourfold guardian kings, heavens of the thirty-three, heavens of Titan gods, heavens of happiness, heavens of the gods of creation, heavens of the gods who create others, worlds of Brahma. Ānanda, to this is called the thousandfold Cūlanika world system. Ānanda, as long as the thousandfold Cūlanika world system prevails till then the thousandfold world system, calls this the two thousandfold middle world system. Ānanda, as long as the two thousandfold middle world element prevails till then the thousandfold world system calls this the three thousandfold and the great thousandfold world system. Ānanda, if the Thus Gone One desires, he announces to the three thousandfold and the great thousandfold world system.

These statements in suttas are closer to fantasy and speculations. How do you explain these with modern cosmology?

You check the validity by seeing for yourself, practising.

Cūlanikāsuttaṃ –– The thousandfold world system
Venerable Ānanda approached the Blessed One, worshipped, sat on a side and said to the Blessed One:Venerable sir, these words I heard from the Blessed One and are acknowledged by the Blessed One: Ānanda, Abhibhū, a disciple of the Blessed One Siki makes announcements to the thousandfold world systems at one and same time from the world of Brahma. Venerable sir, the Blessed One worthy and rightfully enlightened, making an announcement how far could you be heard? so how you confirm the validity of above statement by seeing.

Where is the world of Brahma( a Hindu concept) and thousandfold world system. This is much closer to speculations. There are many more example like this. Refer; "aggajanna sutta" about evolution of humans.

That's not that crucial for the goal of Liberation. Understanding the 4 Noble Truths is.

Can you guarantee the accuracy and validity of the following interpretation of Buddhism about psychopathic terrorists: "Don't kill them just cure them".

Do you approve kill all terrorists if there are possibilities of transform them?  What I try to confirm is "hate is not conquer by hate-that is an universal law- yes this is accurate and right. I totally agree with it. That's a fact.

That's not that crucial for the goal of Liberation.- So why is it in scriptures. What is something out of for the goal of liberation? Do you mean is it just speculations?

Sometimes "heart" just means innermost, core or even mind. It doesn't necessarily mean that organ that pumps blood around the body. If it's the word citta, it basically means mind.

Some times mean not always. mind and heart are totally two different words. you are bending the word by arbitrary.

In Japanese, there is the word shin which literally means "heart/mind".  In Pali, citta means the same.

then what about "citta" and "hardaya" refer my question  thoughts in heart

Wow, you sure got the wrong idea about the superficial packaging of the Tipitaka. "Thoughts are generated in heart" is obviously made with poetic licence and is more something to ponder. Too much intellect will give you wrong view, wrong view and more wrong view.

Hrdaya in Sanskrit has also has multiple meanings.  It can mean "heart" as in heartwood or "essence" e.g. Prajnaparamitahṛdaya or The Heart of the Perfection of Wisdom, heart as in the organ, the mind or spirit, etc.  Etymologically, it just means hrid = center, daya = thus.

By practicing meditation, sila, panna :) don't fool yourself by the intellect that enjoys to read thinking it knows. That's reading and doubt. Meditate. Then doubt.

Read the instructions. The gradual training is many times enumerated in the Suttas. You must have come upon it. There is all you need to verify by yourself without the need of someone else to approve it for you.

I think you are forgetting that those world systems, mythology about the creation and evolution of man, gods, Brahma, etc. were all 100% real to the people of the Buddha's time based on what information they had.  If it makes it easier for you, feel free to reimagine them with the scientific terminology of today.  My expectation, however, is that in 2,500 years, all of those cutting edge theories are going to seem at little quaint, dated, and mostly likely wildly, wildly wrong.
What doesn't change, however, are the core principles of liberation.  These are not dependent on any creation story (as the truths of, say, Christianity are) but are instead derived from direct insight into how suffering is caused by craving.  While you are unlikely to meet any Nagas anytime soon, you are guaranteed to find yourself facing down all of the obstacles to liberation mentioned in the suttas.  The means given for overcoming them will also remain valid so long as there are humans able to hear them.

How do we guarantee the accuracy and validity of Buddhist scriptures?

We guarantee it by the mukkhapātha tradition and inherit study tradition of ancient theravāda society. We strongly keep these traditions through over 2600 years of buddhism's lifetime.
There were too many rules in vinaya, suttanta, and historical evidences showed the ancient theravāda tradition has being serious to protect the original pāli cannons by reciting and memorizing.

Some of these statements [seem] closer to fantasy, supernaturals, assumptions and speculations;

How do we guarantee that fantasy, supernaturals, assumptions and speculations in sutta are not buddha's teaching?
Buddha was not Galileo Galilei, who died because of annihilationism. Buddha teaching is in the middle of eternalism and annihilationism. So, until the fantasy, supernaturals, assumptions and speculations can be possible by the logics, causes and effects or dependent origination (not only by sensual evidences), no need to deny them all.

and few are false statements (e.g "thoughts are generated in heart" is mentioned in Abhidharma).

It is just the western bad reading and studying system that make misunderstanding like that.
The fact is nothing conflicted between "thoughts are generated in heart" of abhidhamma and "thoughts are generated in brain" of biology.
Because abhidhamma taught "thoughts are generated in heart, and that thoughts (and kamma, utu, āhāra) generating brain (cittajarūpa), too".
So the psychology:

positive thinking has a lot of health benefits.

And the medical profession:

Most of the tension that occurs in your brain comes from negative thoughts that ruminate in your head.

If you have the question more about the vegetative state or  the amnesia-patient, see my answer in this topic.

Also information extracted from Buddhist scriptures are mixed with Hindu concepts as milk and water.

The buddhist scriptures trying to fix the problem formed from  Hindu concepts.  But you biasing. So you concluded and decided like "Buddhist scriptures are mixed with Hindu concepts as milk and water".

(most of original Buddhist scriptures were destroyed in Thakshila).

You were wrong. Buddhist scriptures keeping by mukkhapātha tradition]1 and inherit study tradition of ancient theravāda society. So, where is ancient theravāda generation, there is Buddhist scriptures. Therefore, fire can't burn ancient theravāda's buddhist scriptures.

In the kalama sutta it mentions that to completely depend on scriptures is useless.

In vinaya rules, kīṭāgirisutta, too many sutta[1][2] and ancient tradition, buddhist people must recited, memorized, and understood pāli scriptures. So, you are misunderstood kalamasutta. In ancient theravāda tradition these whole scripture evidences must not conflict each other because while reciting the answer will appear in each evidence context. Who misunderstood them as conflict each other, he showed himself that he never recited, memorized, and understood tipitaka.
For kalamasutta, it's context already showed "don't just blind faith in scriptures, but comprehension the fact benefits that you can get from the scriptures".

So how it can be verified statements exactly from Buddha himself (not as a label or maintain faith) just to get progress of right learning and confidence?

Act like buddha taught in kālāmasutta:

Practice yourself to translate whole pāli scripture, included
abhidhamma, commentary, and sub-commentary.
Aovid from the other's translation,
but listen them all as much as you can without any bias, although
you never ever trust them.
Decide them when you perfectly and completely studied and understood
their aspect and evidence.

In my experience, I studied pāli then recite, memorize, and comprehension some important sutta by myself before decide to translate each word meaning in each sutta.
I read commentary directly. I study very simple parts of science, biology, physic, and chemistry.
I often make research of the anti-abhidhammist's evidences.
So, I still stand by the ancient theravāda tradition with a very strong decision, because I still trying to listen and prove every evidences which I can from every teachers, not just the ancient theravāda tradition teachers, and the best benefit still being in ancient theravāda tradition.

Buddhism has history of 2500 years, and scriptures were produced around 300 years after death of Buddha. So how do we guarantee the accuracy and validity of thousands of Buddhist scriptures?

The physical scriptures produced around 450 years, but the study system produced from buddha's living time. You can make your own assumptions. But I will trust just the evidences, history, and appearing culture.
Why the western buddhist professors and students usually stand by the assumptions more than the evidences? Because of their bias about the suffering, such as Crusades or dark age, from their ancient religious, right? Do they forgot that buddhism is not their ancient religious?

Wisdom needs to be  balance with faith. Too much faith in only materialism and only what can be proven to the world is a recipe for one lopsided and heartless religion that  is not very good at cultivating peace and happiness for it's congregation.

Those with no faith will probably not find the value in the Eightfold Path.

Any relationship to the Vedas or Brahmin concepts is usually the Buddha making fun of those concepts or twisting them around to make a different meaning.

There are no guarantees. The scriptures are merely guidelines to show how one can practice to make good habits and undo bad habits for the purpose of getting what every human being wants at the end of the day: Happiness and peace.

The more a certain teaching of the Buddha is repeated throughout the suttas, the more likely that certain  teaching is an authentic teaching from the Buddha. I suppose that is just common sense.
May we all find peace and happiness and be overflowing with metta in all directions...

Several answers.

First is the Sangha. If I have  question about Buddhism, about what a sutta means, I'd want to look for some other peoples' opinions of it first, before my own.
The sutta you quoted (AN 3.80) is not translated on AccessToInsight nor on Dharmafarer (though it is on SuttaCentral).
I only infer from that they consider this sutta to be relatively unimportant, not the most essential sutta -- see also the topic Chronological or other sequence for beginners on this site.

Academics have tools to try to answer this question. There are academics who investigate whether things were really written by Shakespeare, for example, or whether a painting is by Da Vinci.
I think a good example of that is the (academic) paper which I referenced and summarise in this answer.
See also Which suttas in the Pali canon are relatively early or late?

The Buddha himself is said to have given an answer to this question. From the Maha-parinibbana Sutta:

Then the Blessed One said: "In this fashion, bhikkhus, a bhikkhu might speak: 'Face to face with the Blessed One, brethren, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation'; or: 'In an abode of such and such a name lives a community with elders and a chief. Face to face with that community, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation'; or: 'In an abode of such and such a name live several bhikkhus who are elders, who are learned, who have accomplished their course, who are preservers of the Dhamma, the Discipline, and the Summaries. Face to face with those elders, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation'; or: 'In an abode of such and such a name lives a single bhikkhu who is an elder, who is learned, who has accomplished his course, who is a preserver of the Dhamma, the Discipline, and the Summaries. Face to face with that elder, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation.'
"In such a case, bhikkhus, the declaration of such a bhikkhu is neither to be received with approval nor with scorn. Without approval and without scorn, but carefully studying the sentences word by word, one should trace them in the Discourses and verify them by the Discipline. If they are neither traceable in the Discourses nor verifiable by the Discipline, one must conclude thus: 'Certainly, this is not the Blessed One's utterance; this has been misunderstood by that bhikkhu — or by that community, or by those elders, or by that elder.' In that way, bhikkhus, you should reject it. But if the sentences concerned are traceable in the Discourses and verifiable by the Discipline, then one must conclude thus: 'Certainly, this is the Blessed One's utterance; this has been well understood by that bhikkhu — or by that community, or by those elders, or by that elder.' And in that way, bhikkhus, you may accept it on the first, second, third, or fourth reference. These, bhikkhus, are the four great references for you to preserve."

The Abhidamma isn't the same as the suttas. Both the Abhidamma and the Suttas are parts of the Tripitaka (the Pali and/or Theravada canon), but I think there are Buddhists who prefer the suttas.

Beware of translations. A word like "Heart" or "World" or "Atom" has a modern meaning. When suttas are translated into modern words, they may seem to make less sense (e.g. because you don't think with what you'd now call a "heart"). Consider though that the statement probably made sense in the original time and language, and that the translation is an approximation ... it's partly up to you to try to understand what it meant originally. It's also well to recognise that there are several translators and translations, some may make more sense to you than others.

A reason why you may find Buddhism interesting is that it's helpful, useful, and self-evident (by which I mean that it make statements which accord with your own experiences).
So take the parts of it that you find helpful.

It's worth studying what the suttas actually say, I think they're carefully expressed.
For example you wrote,

In the kalama sutta it mentions that to completely depend on scriptures is useless.

The Kalama Sutta might say something a bit like that, but it doesn't say exactly that. I think it's worth considering exactly what it does say.

I've seen at least one "cosmological" sutta (the Aggañña Suttaa) described as being a parody of the Vedas, or as Buddhist mythology (I guess that's a matter of opinion which some other people would not agree with).

The basics of Buddhism is the Triple Refuge. The 2nd Refuge is refuge in the Dhamma or the Teachings, which is officially & completely defined as follows:

Svākkhāto bhagavatā dhammo sandiṭṭhiko akāliko ehipassiko opaneyyiko paccattaṃ veditabbo viññūhīti
The Dhamma is well expounded by the Blessed One, directly visible, immediate, inviting one to come and see, applicable, to be personally
  experienced by the wise.

Everyday, the above verse is chanted in every Theravada monastery by the monks & nuns. Anything that falls outside of the above definition of Dhamma is not the True Dhamma.
The only people with right learning & confidence are Stream-Enterers & above, who have experienced which teachings when practised result in Nibbana (freedom from suffering).
As stated in the Kalama Sutta, Buddhism does not have any expectations of unverified belief.

Buddha expounded 84000 different teachings to suit the different types of personality and background. So if one starts exploring, one will find the champion teaching. It is like different cultures in different country. In one country people like durians, but in another country, people find eating durians too disgusting. Thus, one need to find the teaching that suits- not necessarily from reading but also from hearing a Sangha.