I don't think you can. You can battle them in Ruby, Sapphire, and Emerald though.
I think if you get a rematch with Bugsy.
No, you don't battle Steven in HG/SS.
no brenden is in only ruby sapphire and emerald only if they make a remake of it ss and hg are hibiki
no, onlt in ss and hg
ALOT of trainers and gymleaders. Also I want too.
Soulsilver=SS heartgold=HG KK=O.K
In the Battle Frontier. Or you can get it on another game, have a Pokemon hold it, and then send it to SS/HG using 2 DSs or the GTS.
yes. I've done it with both HG & SS.
You can't battle Roark in HG/SS. If you saw that video on YouTube that giancarlomango11 made, it is all a hack.
You have to trade it from Diamond, Pearl, or Platinum. You can't evolve Eevee into it in HG/SS.
yes,as long as you have bought a new HG or SS
Depends on whether or not you're in the Battle Frontier.