Basically in Apprentice, there's a ChaosWorld type effect that like any EnchantWorld; it affects all players. Then at the beginning of your turn, you roll for a ChaosEffect (the types of rolls are in Apprentice, although I'm sure they're on the Net somewhere). That's pretty much it.
I don't think so. Unless you specify a certain format or whatever, but if it's Vintage Constructed, obviously anything goes. It's basically just a duel with the chaos stuff thrown in.