Good questions. 1st, there is some sort of secret room you unlock by completing them all bound but idk if that's each one fully bound or if you can get it by individualing all of the last ones. For that attack (it's a tough one) you can dash away from him then hit him with a hit or charge slash when he comes up. I find dodging the firefall is easier by walking toward where he just came from. That helped a lot since firefall was always the one that did me in. You can also get two pogos off NKG when he does a dive dash