Transmogrifying questions I have.

I don't know where my thread from earlier went, I believe I did nothing wrong... So if someone can please answer these questions I would appreciate it.

1.) Will we be able to tell PvP and PvE gear apart?
2.) Will we only be able to transmogrify specific class armor? (Death Knight for me.)
Or since I'm a plate class, will I be able look like I'm wearing Paladin or Warrior gear?
3.) Will we be able to honestly transmogrify anything? Like nooby looking armor with awesome stats? (Let's stay starter armor.)
4. Will I need full sets of certain armor to transmogrify it? Or let's say, if I just have a a cool helmet from a previous Tier, would I be able to just have the helmet changed?