No. Zecrom is unavailable in Pokemon Black. You will need Pokemon White to get it.
First, you need to migrate your Pokemon in Sapphire to Pokemon Diamond, Pearl, Platinum, HeartGold, or SoulSilver. Then, you need to migrate those Pokemon to Pokemon Black.
Unless you cheat, you can only obtain Reshiram in Pokemon black. You will need to trade to Pokemon black if you have white for zekrom to be in Pokemon black.
You can't catch it in Pokemon Black. You'll need to trade for it from Pokemon White.
A pokemon that knows Charge can, but you will need to get a pokemon from Pokemon White that knows Charge. Same goes for those who own Pokemon White, you will need to get a pokemon that knows Charge from Pokemon Black to activate the time machine.
You would need to trade for them from Pokemon Black or White, for they are not available in Pokemon Black 2.
You'll need to trade for it, because Duosion isn't in Pokemon Black. It is only in Pokemon White.
You'll need a Pokemon and a Poke Ball.
There's no password to get a Porygon in Pokemon Black. You'll need to trade from Pokemon White.
Get a Sandile
You'll need to trade for it from Pokemon Black.
Reshiram is not in Pokemon White you need to trade either with Pokemon Black or Pokemon White 2.