BC Amateur rules vs UFC (more accurately, Unified MMA) rules: The biggest differences are the rounds will be 3 minutes long instead of 5 minutes, and elbow strikes are not permitted. Otherwise, pretty much the same.
Ring vs. "Octagon": As you saw in the videos, fight is in a cage. I don't know how many sides it has.
Favourite fighters: this is tough. I first got interested in training after a friend showed me some Sakuraba DVDs, so that's certainly an inspiration. My PokerStars avatar is José Aldo. Then there's B.J., A. Silva, all the obvious choices. I don't know. All the name pros are so amazing. I mean I've trained with guys, and they seem like absolute beasts to me. Then they go out on a big show and lose to a guy. Then
that guy loses to some marginal UFCer, who gets pasted by a legitimate UFC contender. It's so tough to pick favourites when I think about what amazing athletes they are compared to me; I mean, they're all just so great.
Leg kicks: Anyone who has ever been hit by a leg kick so hard they couldn't finish the sparring round has respect for them. And that's almost everyone who has done enough sparring.