Short answers, pulled from the story.
Street Fighter Alpha Anthology includes five default games: Warriors' Dreams (1995), Alpha 2 (1996), Alpha 3 (1998), Alpha 2 Gold, and Super Gem Fighter Mini Mix (1997). Two additional titles, Alpha 3 Upper and Hyper Street Fighter Alpha, can be unlocked through gameplay.
Hyper Street Fighter Alpha becomes available in Street Fighter Alpha Anthology after the player completes all the default games and Alpha 3 Upper at least once. It is a Versus and Training mode-only version of Alpha 3 where players select between different character versions from across the Alpha series.
The Japanese version, titled Fighters Generation, defaults to the Japanese arcade versions of Street Fighter Zero 2 and Street Fighter Zero 2 Alpha; North American and PAL releases default to the U.S. Alpha 2 and Alpha 2 Gold. Fighters Generation also includes in-game character movelists accessible by pausing, a feature absent from Western editions, and uses original arcade sales flyer artwork in its menus.
Street Fighter Alpha Anthology is one of a handful of U.S. PlayStation 2 titles with hard drive install support. Using an original fat PS2 with the official HDD installed, players can load 2 gigabytes of data onto the drive, eliminating virtually all load times.
In the Street Fighter Alpha Anthology version of Alpha 2 Gold, Cammy is available in all game modes, including single-player Arcade mode, where she has her own storyline and ending. Earlier console releases of Alpha 2 Gold limited Cammy to Versus and Training modes only.
Super Gem Fighter Mini Mix appears in Street Fighter Alpha Anthology partly because of its role in the 2000 animated film Street Fighter Alpha: The Animation, in which Sakura is shown playing it on a WonderSwan gaming handheld. It is a 1997 CP System II arcade fighting game featuring more than ten playable characters drawn primarily from Street Fighter Alpha 2.