I think if you complete c sides it should be 120% or something to that extent

Wouldn't you count crystal heats and b side collections in 100%? And yeah there's multiple save files so it should be easy to require new file. Although on the other hand it really doesn't matter since you gain nothing from replaying after beating the game. Although there is a begining cutscene that would take up real time.

Yeah the restore when changing frame is an intended game mechanic you use it a few times during the game to get extras.