The snow doesn’t happen as far as I know. It certainly didn’t when I was there over Christmas and New Year.
The parade runs until New Years Day, so do the ride overlays like Jingle Cruise. But the party overlays this year are different in that they are only for the parties. So I don’t know if they will continue or not.
From what I’ve read, you’ll get to see the Christmas parade but only in the daytime whereas they have it at night during the parties. I was curious, too, about the party snacks but have not been able to find an answer.