The short legs is a breeding tactic used by breeders for god only knows what purpose. Cats need to be able to be nimble.

Cats have whiskers all over their bodies so anything, outside of a collar prevents them from sensing things around them as they should. As far as belly rubs, a cat will expose it's most sensitive body parts to those it trusts.

And the reason she behaved the way she did when you first got her is because she was scared. Cats will lash out and or hide in unfamiliar settings and situations. I recommend you watch The Kitten Lady and Jackson Galaxy on youtube.