@poljakovski,
I don't mean to be unkind to any of the respondents but we all have to consider, seriously, just what the context is. It doesn't help ESLs/EFLs to deal with grammatical constructs in a vacuum. Life, and therefore language do not exist simply on a page of paper.
CONTEXT CONTEXT CONTEXT CONTEXT CONTEXT CONTEXT !!!!!!
Quote:1) "She FELT very tired, and while she was finishing her studying, she fell asleep." or "She WAS FEELING very tired, and while she was finishing her studying, she fell asleep" is the correct one?
It could be either 'felt' or 'was feeling'.
The last portion could be either 'fell asleep' or 'was falling asleep". The first would denote a one event. For example, she fell asleep, stayed asleep for some time, woke up or was woken up by someone and went off to bed or later resumed studying.
'was falling asleep' would describe a situation where she was continually nodding off.
Quote:2) Is this sentence possible: "Sally didn't go to a boxing match before." ? Or the verb form can only be "hadn't gone" ?
Yes, the first is most certainly possible. English speakers sometimes do use the simple past to describe past experiences; traditional grammar says it has to be done with the present perfect, ie. "Sally hasn't [ever] gone to a boxing match before".
When the simple past is used, you'll often see an 'ever' included, as in,
"Sally didn't ever go to a boxing match before."
The past perfect "hadn't gone" sounds a bit odd as a stand alone example without some greater context.
Quote:3)"For a week we CLIMBED/WERE CLIMBING higher and higher, following the map, which Tom STUDIED/WAS STUDYING from time to time." Which verb forms are correct?
Both would work in certain circumstances. In some situations, the choice of verb form can express a different nuance.
Remember,
CONTEXT CONTEXT CONTEXT CONTEXT CONTEXT CONTEXT !!!!!!