As far as I remember, Degrassi has no individual movie. I checked the archives and it was released as 8x19. This needs to be fixed, but I currently don't have enough time.

Looks like there was conflicting info on their website, here they never included it in the season 8 listings. In the galleries section, the movie's photos are also sorted in the special event section opposed to with the season 8 episodes.

It was heavily treated as a movie here

Just noticed there's an entry for it in the Specials too, along with Degrassi Takes Manhattan

As for S14E25, MTV described episode 23 & 24 as the finale episodes here, while "Don't Look Back" is called a 2 hour special so if not entered as a movie it should probably be a special