nothing game wise um you gain the satisfaction of beating one of the toughest trainers in the game
you get to fight ash, but he apears as pokemon trainer red.
You get another coloured trainer card. If it's gold, you get a black Trainer Card.
No there is not a trainer editor in Pokemon black 2 or Pokemon white 2
Yes.
a lot
No one
you can not
I think you mean Electivire. Unfortunately, there are no trainer with an Electivire in Pokemon White. There is only one in Pokemon Black which is in Black City but Black City is not in Pokemon White.
A trainer in route 23 has a rufflet
A trainer that has an Axew =D
Reshiram. But if you make any other Pokemon stronger than it by level, yes, then it will be that Pokemon. But if you look to it by the side of legends and legendary power, it is Reshiram.
nothing, but Congrats! u got a black trainer card!