A few clarifications:
Last Arcs are done by EX-Shielding while in Blood Heat. Most characters need to be on the ground, but some characters (Arcueid and Mech-Hisui are the only two I can think of off the top of my head but I know there's more) need to be in the air. Most, but not all, Last Arcs hit the opponent with Circuit Break, which kills their circuit and makes it so they cannot generate any for a short time. There are three moves that cause Circuit Break that are not Last Arcs, NA's 6236C, NAC's alternate Arc Drive, and one of G666's moves. Cats get all the perks.
EX-Shielding is activating the shield within a very short timeframe of the attack - probably somewhere in the timeframe of "single-digit frames" but I don't know offhand. Shielding is having the shield active after the time limit for EX-Shield. It takes longer to recover from a Shield, and keeping a Shield up eats up circuit like mad. EX-Shields cost no circuit. Back in RE-Act, there was only the "short time limit" Shield, and it was just called "Shield." They added the new name and the new version in AC.
Kohaku's pretzel move is baffling. I also thought it was an actual pretzel (1632143) or something. Who knows!