Yes
Yes. After you beat the main story, you can migrate from daimond, pearl, platinum, heartgold, and soulsilver versions to black and white
Not directly. You have to migrate to diamond pearl platinum heartgold or soulsilver first and then after you beat the elite 4 in white you can connect 2 da systems to migrate from diamond pearl platinum heartgold or soulsilver over to Pokemon black or white.
You can't migrate from HeartGold to Ruby. But it can be the opposite. Pokemon can be migrated from Pokemon Ruby to Pokemon HeartGold.
Yes, you can migrate Pokémon into HeartGold.
You must migrate it from Diamond/Pearl/Platinum/Heartgold/Soulsilver.
You can migrate it from a copy of Diamond, Pearl, Platinum, HeartGold or SoulSilver.
You don't you have to migrate to get sinnoh pokemon.
Migrate raquaza
You can't; you need to migrate one over from Diamond, Pearl, Platinum, HeartGold or SoulSilver.
As far as I know, Pokemon on Pokemon Black and White have to stay on those games, as for Pokemon HeartGold and SoulSilver, you can not only migrate Pokemon from earlier generations of games, you can also trade with Pokemon Platinum and Diamond and Pearl. Still, the Pokemon on Pokemon Black and White look cooler! :)
migrate and trade
you need to migrate it from sappire