1 John 3:20 what does it mean "He knows everything" according to Calvinist Single Predestination? This question as a continuation of my question here, because the question before is not "tight".


  1 John 3:20
  
  For God is greater than our hearts, and He knows everything.


Trying to put my point of view in Calvinist style, I have the verse sentence something like this : He knows everything before the Creation

Now the question is, before the Creation - He knows everything :


X. after He planned all things which absolutely are going to happen
absolutely from A to Z? or
Y. before He planned all things which absolutely are going to happen
from A to Z?


When I myself have X as an answer, then to be honest I can't see something wow! about "God knows everything", as to me this is more about God Omnipotent. 

But the worse is that I can't see that "God knows everything", because the conclusion then "before He plan, He doesn't know yet". This leads me to disregard option X, and try to look option Y.

But option Y to me is absurd because if He knows everything which absolutely are going to happen from A to Z (He knows that He create Adam - He also knows that Adam is --for example-- in heaven) - then there is no option to make a plan, there is no option to have "If ... Then I ..." or "If I ... Then ... " rule. 

And the worse is then God is not Omnipotent as He is unable to change all things which He knows absolutely are going to happen from A to Z. At the time of Creation and after it, God only follow what is "already written" ("already written" = all things which He knows absolutely are going to happen).

I ask to the Calvinist Single Predestination, because option X to me is more "fit" with Double Predestination although it leads me to conclude that "God doesn't know everything" before He plans it.

So disregarding X and Y, I would like to know first what does it mean "He knows everything" according to the Calvinist Single Predestination ?
The traditional Calvinistic understanding of the relationship between God's knowledge and God's decree relies on an important distinction, which I'll briefly explain, then present to you how Historically Reformed Confessions articulate the relationship. 

When we are talking about "time" before creation, we must understand that "time" in any traditional understanding doesn't make much sense. We cannot say that God went from a state of not knowing all things to a state of knowing all things, nor can we say that there is any meaningful sense in which God had not yet decreed all things, then went on to decree all things. 

So when we talk about things happening "in eternity" we must do away with chronological distinctions, and rather talk in term of "logical priority". Which is logically necessary for the other?

Now for the historically Reformed understanding, as presented in the 1689 London Baptist Confession of faith (it's the same in Westminster): 


  3.2 Although God knoweth whatsoever may or can come to pass, upon all
  supposed conditions, yet hath he not decreed anything,
  because he foresaw it as future, or as that
  which would come to pass upon such conditions. 


Let's break this down. In 3.1, the confession says God decreed all things, then here the confession explains that relationship. While it affirms that God knows all things, the confession unequivocally argues that God's decree is not dependent upon that knowledge. God did not decree anything on account of his divine foreknowledge. 

Therefore, we would say this "God's decree is logically prior to God's foreknowledge", or alternatively, "God knows all things because he decreed all things." 

So this answer is something of a framing challenge, I do not believe you are asking the right question. Whether, as a Calvinist, you affirm Single or Double Predestination, this ought to be your view on this relationship, and it is the view shared by historical Single and Double proponents alike.