Not like I'm an official and know stuff but I'm pretty sure the answer to that last one is yes.
I can't wait to throw a finishing buster at an incoming beam, and then shoot a generic beam behind my buster... finally Trunks can PS!
Why help out in a PS even without the kill? Well, it's just cool. A lot of the features in the game are just sort of unnecessary extras. Actual power struggles are rare, and block struggles are even rarer, since most people find dodging more effective. But if I know my opponent is pretty bad or whatever I like to do these things, just cause they're just cool, and were made to make the game feel like DBZ, and they do :laff: