if you mean change from a fossil you can get cranidos and shieldon. once you get the national dex you can find any fossilised Pokemon from old generations like lileep or ominyte
YOU need Pokemon ranger for that YOU need Pokemon ranger for that
you dont need any specifics pokemon, you need the national pokedex.
No. Zecrom is unavailable in Pokemon Black. You will need Pokemon White to get it.
you need the same Pokemon to evolve it.
First you need 2 Nintendo DS. Then you need a link cable. Then you can trade Pokemon!
On www.serebii.net, click on pokedex and search the Pokemon you want to see. All Pokemon need a different amount of steps. With the pokedex you can see that. You need to know what Pokemon it is!
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.
Pokemon and pokeballs
You'll need Pokemon ruby. If you mean ruby to sapphire, then you'll need both games, two gba's, and a link cable.
you need to find 210 Pokemon to complete the pokedex
No, you do not need any special Pokemon. Jirachi is an event Pokemon which you get from special Nintendo events.
you need 200 Pokemon to fill the whole pokedex