The two builds come courtesy of the popular Spyro content creator Hwd405, who collaborated with the preservationist group Hidden Palace to dump both prototypes and document the changes that were present from the final retail versions.
According to the Hidden Palace site, the newly discovered prototype of Spyro: Year of the Dragon is dated September 4th, 2000, which means it is from just 10 days before the final build. Despite that, though, there are still a ton of fascinating differences present. For instance, it features an entirely different soundtrack, missing sound effects, alternative object placement, and audiovisual changes across various cutscenes. There is also data present on the disc from earlier builds as well, including a test level for the Kangaroo character Sheila, where she has horns similar to her original concept art.
The Crash Bash prototype, meanwhile, is labelled August 23, 2000, placing it 2 months before the earliest final build, and features a ton of unfinished/placeholder levels, menus, and icons.