Short answers, pulled from the story.
The Street Fighter Alpha Anthology includes Street Fighter Alpha: Warriors Dreams, Street Fighter Alpha 2, Street Fighter Alpha 3, Super Gem Fighter Mini Mix, and a remixed console-exclusive version called Alpha 2 Gold. The compilation also contains two secret games called Street Fighter Alpha 3 Upper and Hyper Street Fighter Alpha that unlock after completing all default titles.
The Street Fighter Alpha Anthology arrived in 2006 as a digital time capsule and was released in Japan as Street Fighter Zero: Fighters Generation. The Japanese version featured each of the Street Fighter Zero arcade games including the Japanese arcade versions of Street Fighter Zero 2 and Street Fighter Zero 2 Alpha as part of the default lineup.
The narrative structure of the Alpha series defied linear logic by moving backward and forward depending on which game one played. Street Fighter Alpha 2 arrived in 1996 and placed its events in the year 1987 while Street Fighter Alpha 3 moved the story forward to 1989.
The compilation included an HDD install feature that allowed players to install 2GB of data to the HDD on an original fat PS2 console to eliminate virtually all load times. The anthology also featured an in-game character movelists that could be brought up by pausing in the Japanese version and an options menu to create custom revisions of the game.
Capcom created the anthology to unify a fractured series before the release of Street Fighter III and to preserve versions that were otherwise lost to time. The compilation preserved conflicting timelines and regional differences to allow players to experience the contradictions and nuances of the franchise's global expansion.