iirc you get a free month of playtime if you purchase a boxed copy of the game whereas if you buy the key only online you dont get the free month.

I think it was Circuit City that has the battlechest (wow&bc) bundle for $39.99 and you get 2 free months of playtime. 1 for the vanilla wow purchase and another for the burning crusade expansion.

And no you cannot grant levels across the factions. You have to party together the toon that is granting and the toon that is being granted to.