If my current world is Wonderland 1 and I play a copy of a world previously played (and still in play) do I still discard? Does WL power as it's being replaced? What about if I play another WL on top of the other?

Am I playing Behemoth right in saying that if he is on a world and a battle takes place on that world, then the player must use all his friends, but the damage can be assigned as he sees fit?