yes, you can with two Ds. Just put Fire Red in one Ds and SoulSilver/HeartGold into the other Ds and then just meet each other in the union room. For two Ds, just borrow one from a friend or use a siblings.
no you can not, you can only get ho-oh in Pokemon heart gold or soul silver, or you can get it in global trade.
No. You have to migrate six Pokemon from GBA games once you reach Fuchsia City.
sorry you have to trade it to Pokemon soul silver
Either have it as a starter in Pokemon Gold, Silver, Crystal, Soul Silver, or Heart Gold. In Pokemon LeafGreen and FireRed you'll need to trade a Pokemon for it. Also in Pokemon Sapphire, Ruby, and Emerald. In Pokemon Diamond, Pearl, and Platinum you have to trade a Pokemon for it. Hope this helps!
No. You can only transfer firered Pokemon to soul silver.
trade it from Pokemon soul silver
Pokemon center.
you can get mewtwo more than once if you get it in firered or leafgreen and trade it via pal park
These Pokemon are ONLY available through trade from leafgreen and firered without action replay. One exception is you can get one of them by beating RED (ash) in Mt. Silver on soul silver game.
none
You can trade your Pokemon for a celebi.
you have to trade it from diamond to soul silver and you can't actually catch Roselia wild in Pokemon soul silver.