Hi Optional and welcome to the Org!
1 We don't see Donnie but Ricky calls out to him after he hollers about the cable and calls him Danny.
2 Yes IMDB is wrong, Cart Boy was made after the 1999 movie,as per Clattenburg's commentary. It was a way to introduce the "Bubbles" character, called Darren in Cart Boy. Mike Smith would goof around as his Bubbles character while he worked on the 99 movie and the boys liked it.
3 Yes unfortunately it is mislabeled, it is the 99 movie. Hearts of Dartmouth talked about One Last Shot and the original movie, and after that for some reason a lot of people seem to think they were the same thing but they are not.