Are animations with interpolation allowed if the final result is still aligned to the pixel grid?
Nearest neighbor interpolation has generally been accepted as long as it aligns to the pixel grid. Bi-linear interpolation starts to play with opacity of the colors, so unless you are trying to mimic the screens ghosting, I would generally avoid. Games have to have pretty egregious sub-pixel movement or be blatantly ignoring the resolution rules to get disqualified. If you upload an example of what you are talking about I could give you a more definite answer.
Is it allowed to generate graphics procedurally during or before the game runs
/ prerendered graphics?
Since we are not trying to get the game to run on the actual 3310 whatever modern features hardware/engines have you can use. Unless you are trying to be as accurate as possible we are simply trying to make a game in the spirit of the original phone.
I hope that answers your questions and feel free to ask more or for more clarification on any of this. I am happy to help!