I'm using the guidebook to get treasure chests and there are some spots where it says (mimc) but I can't seem to find anything there, does anyone know what to do with these mimic points?

Well in BBS mimics are treasure chests with Unversed in them, so I would think in DDD they would be heartless in treasure chests, although I could be wrong

To my knowledge, there is one fake chest in every world (except TWTNW), Sora/Riku would tap it as normal but instead of items etc it'd be a Jestabocky.

I haven't see mimic yet.

I go there bu I haven;t seen them yet another, on another note do portals appear at random and are they important or good for anything. I can't see any use for them really.

A mimic is a chest that contains no items but if you open it dream eaters will spawn