So everytime i speedrun GTA III or any other GTA that doesnt support fullscreen livesplit and wsplit end up flickering the whole time except when im tabbed out from the game

what do u do to record these games?

I don't know how to fix it for fullscreen, but I run it in windowed mode with D3Windower: http://pcgamingwiki.com/wiki/Glossary:Windowed#D3DWindower