Differences: 别的 vs 其他 vs 另外 (other) Well, the question is in the title... I'd be very thankful for an explanation, but also:

Could you give examples of cases where they are and are not interchangeable?

Can I use them for "where are the others/is the rest?"? Or "other than that, I'm not sure"?

When in doubt, which to use? (which is most general?)

This question is similar to this one but I'm also curious about 另外, and in the general sense, not just with 人. I also found reddit (useful but frozen) and Chinesepod (too expensive for one answer).
When talking about English and Chinese, we will find that there are many English words stand for more than one meaning in Chinese, such as other(s) in Chinese. It means 其他 or 其它. Although they look like, they are quite different.
Chinese: 其他/其它
pinyin: qí tā
meaning: other(s)

Similarities of 其他 and 其它

1). Same pronunciation
Both 其它 and 其他 are pronounced qí tā.
2). Same meaning
Both of them mean “other” or “others”.
3). Same part or speech
Both of them are pronoun.

Difference between 其他 and 其它

其它 and 其他, generally speaking, are almost the same. They differenciate with each other in two aspects.
1). Indicate different objects
其他 can refer to any creatures, including human, animals and stuff without life, such as 其他学生(other students), 其他城市(other cities), 其他电脑(other computers). While 其它 can’t refer to human, for instance 其它动物(other animals), 其它桌子(other desks).
2). Appear at different time
In the beginning, there is only 其他 available. Gradually, 其它 was created out of the actual requirement. Hense, 其他 emerges before 其它.