tiny creatures and movement

So I'm going over some stuff and i realized i didn't know some of the rules for tiny creatures in combat... I'll just list out my questions.
1. Can two tiny animals flank a medium person?
2. Does moving through a tiny animal's threatened square provoke and AoO?
3. Does a medium person have to roll an acrobatics check to move through a tiny creature's square?
4. Can I build a wall of chickens in between a fighter and my fellow caster?

1) Only if they are either wielding reach weapons, or have a special ability that provides it.
2) Yes.
3) Yes.
4) How? Won't they just move away when their turns in the Initiative order comes up?