You can use any electric or leaf type pokemon i think
You can either: A. Beat the elite four and you get it right before you fight N. B. Use an action replay and use a Pokemon modifier code.
Mostly Pokemon that have high stats, example: final evolution of strong Pokemon and Reshiram or Zekrom. check bulbipedia for Pokemon with high stat totals
You must catch Reshiram or Zekrom, for the game to proceed. You do not have to directly use it in the battle against N though.
not until you beat zekrom in black or reshiram in white. then some might appear in places which require you to beat the game to access
I prefer you use Reshiram or Zekrom or level 100 pokemon. You could also use big legendary pokemon like Dialga,Palkia and Girantina and so on. Or level 90's.
No you can't unless you use cheats here are the games POKEMON BLACK VERSION: Reshiram POKEMON WHITE VERSION: Zekrom
No. Once you beat the Elite 4 you have to go into N's throne room. Zekrom will appear. Your best option would be to use the Master Ball to catch it.
mewtwo is because in the first movie it say that mewtwo is the strongest Pokemon
you have to get alot of rock type freinds and use picachu
Either use an Action Replay or trade with someone.
you can't. trade with someone who has Pokemon white or use gts
In white you use the master ball in black you trade