Can confirm GTA 4 runs on a 13inch mbp late 2015. You need to download the xliveless patch (google for a link), and you'll need to place it in the EFLC folder in your c drive. Mines in my steam downloaded games directory, but it will depend on how you got the game. Once the patch is downloaded, you need to turn off wifi to get past the splash screen, and then skip the cutscenes as they tend to freeze the game sometimes.