What exactly are the differences between challengers and the other versions?

Challengers has extra Halloween-themed Levels and also multiplayer.

Thanks for the reply. Are the halloween-themed levels timed into the run?

They should be IMO, that's why I think it's a better idea to have a seperate game page for Kao Challengers. In fact, I made one right now: http://www.speedrun.com/kao-ch