[@Red X] For magic, you need only to list prominent spells. If you're a cleric it isn't hard to guess that you have a healing spell or a protection from evil spell, and for a wizard or other such arcane user, it isn't that hard to imagine you having a fireball or Telekinesis spell.

The only thing I'm really going to say No to are "Monster" races. Not Centaurs or Minotaurs, but like Beholders, Chuuls, or like a Bog Creeper.

You [i]can[/i] in fact Multiclass, however do know that both classes (or three, if you're into that) will be weaker than if you were to just do one class.