Oh that's already been explained as Peridot acting funny to appease Lapis (see: Raising the Barn). It's dropped now and the barn is literally in pieces.>>104456968
It's not non-canon, Pearl's VA just said Pearl acted very OOC in the episode which was kind of the point. Mystery Girl turns up wayyyy in the background of an S5 episode called The Big Show. That's all.>>104456304
She does, but I forget the episode where it happens. It's the one where Steven plays Steven Tag with Amethyst and Garnet. Keep Beach City Weird, maybe?