Ground bounce is a special move property that causes them to actually well… bounce. Moves like hawkeye’s OTG freeze shot, Verge’s SH target combo, Haggar’s air pipe, Sentinel and Tron’s j.S, etc cause ground bounce states.
Yes. You are correct. Off The Ground (OTG) capable attacks are ones such as Wesker’s gun, Felicia’s Sand Splash, Super Skrull’s Stone Smite, Sentinel’s :l: Rocket Punch, Wolverine’s slide, and Zero’s lvl 3 Mega Buster.
I’m very much a Marvel newbie, but I think I can answer your question.
I think that the move that you are talking about is his Sentsuizan (looks like a dive at the character that is in OTG status). Zero can actually cancel any move into a level 3 buster. He can cancel the Sentsuizan with a level 3 buster and continue to combo afterwards due to the massive hitstun.