You can't get 100% completion in GTA: San Andreas right now
GTA: San Andreas from Grand Theft Auto: The Trilogy – The Definitive Edition couldn't be finished completely right now. There was a bug that prevented one of derby demolition races. Moreover the side mission was damaging the save.
Recently released patch fixed the bug. But it also removed The Chiliad Challenge side mission on a mountain bike. To get 100% completion you need to finish the race that is now gone from the game.
Rockstar Games promised that the GTA: The Trilogy will get multiple patches, so the completionists will have to wait.
You can find saves and mods for GTA remasters on our site.