My scenes are locked! Can I replay a previously done scene and still collect points?

I'm not sure what "points" you are collecting, but in most situations, replaying a Mastered scene is just as good playing a new scene, i.e. play 48 scenes with discount energy, find 300 objects, find 1400 coins, get 8 "perfect" marks, beat your own score. I think the only task that requires new scenes is earn 2 (or 4) clues.