For A and N Groove, press both Fierce+Roundhouse button at one time, and the Custom Combo will activate for A-Groove, or you will break a stock for N-Groove.
As for C-Groove, I’m not so sure about taunting during the super cause I never did it, but you can cancel a level 2 super in between by inputting anothing special move during the animation or right after the animation.
I swear there are groove specific threads for things like this…LAZY…
Taunting is a special move, so you can cancel out of a lvl2 with a taunt whenever you could with a special. The super has to hit before you are able to cancel. Most taunts don’t do damage, as they don’t hit the opponent. Test which taunts will hit in training, but I doubt it’s even worth it. The amount of damage you would get from a taunt is miniscule at best, and taunting gives your opponent meter.