[Sundae]

Re hung/ hanged. I've noticed that "hung" is more prevalent, probably even correct, in American-English.
It's therefore becoming more common here - probably because we don't hang people any more, so there is less reason to use the term.

I always use the correct (traditional) hanged, and have been picked up on it before. People think it sounds wrong, like referring to a group as a singular entity ("The party was shown round the castle.")

I'm by no means a grammarian, and I do speak and write in the vernacular. It's just interesting how language bends and flexes over time. One generation's slang is another generation's standard.