about rewinding; I am not aware of any game that makes it possible while the game is played.
for Sims2, the only options seem to be these::
-record the game through any means then play the recording. rewinding is possible in a recording.
-exit lot without saving then play it again. some chance of the same events happening again.
about creature appearances; I think the only ways for different sims of same type to look different would be the things that objects could change. in shipped version; plan & change outfits on dressers, change appearance on mirrors/vanities, or University's "Cosmetic Surgeon" (Show Business reward), or OFB's salon chair.