GTA 1991 Mod is a Prequel to San Andreas

gamerant.com:

Following the success of Grand Theft Auto 3 and Grand Theft Auto Vice City, Grand Theft Auto San Andreas built again on Rockstar's series of open world action games. Set in 1992 in a fictional version of Los Angeles, San Andreas took players on the journey of CJ. After returning home for his mother's funeral, CJ discovers that the Grove Street Families have lost most of their influence on the territories of Los Santos. Grand Theft Auto San Andreas is often hailed as being one of the best and most chaotic in the GTA series. However, fans have pointed out that the story of the game sometimes feels as though it's missing something.

As CJ returns home after a long time away, the player relies on other characters to inform them of what Grove Street used to be like and what's changed. With a whole new group of players being introduced to San Andreas through the GTA Trilogy, even more people are now noticing that the events of San Andreas often can feel unexplained or like they're missing something. One team of modders is looking to now fix that problem.

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An ambitious team of San Andreas fans, headed by one deltaCJ, have decided that GTA San Andreas could do with a prequel game to flesh out the world of the game and the story behind it. According to the modding community, GTA Vice City and Grand Theft Auto 3 both received prequel off shoots of their titles shortly after release. Since GTA San Andreas did not receive the same treatment, modders have threatened to release their own version of a San Andreas prequel since.

The mod is currently entitled GTA 1991, and follows the story of Little Devil. Little Devil is a character mentioned by Sweet as having died