The divine spark was given out at the begining of the war (a thousand years before the teaser). By the end, the war had touched everyone in some way and things weren't so neatly divided anymore. All races fought in that final battle.
There was only one language in Heaven. In one of my playtests I have a character who can understand more languages than anyone else in the party (because he's studied hard since Heaven), but he refuses to "speak" them because the idea of a language that isn't the Divine Tongue offends him so deeply.
Ravenloft had rules about spending unspent laguage slots after creation, but they took a brutally long time. I prefer to assume that learning languages during desperate, panicked emmersion is very quick. If you give a good bit of down time between Throne of God and the next adventure (such as A Knife in the Dark) I'd let them spend all their remaining language slots.
I'd let them pick their domains as long as they don't pick one like "evil." DM approval as with all things. I keep the details about Heaven and the Church there vague so players can help shape it how they think Heaven should be. In GerikGnome's game no one has spoke of orders (but the only channeling caster left the game). In the Harp playtest the cleric came from an military order of the Heavenly Church that dedicated itself to the war.