Most "GTA 5 CSO" links you find online fall into two categories: Modded Versions
The format is a compressed ISO image, originally popularized for the PlayStation Portable (PSP). In the context of Grand Theft Auto V
A file is a format used for PSP games to save storage space. Because a real version of GTA 5 is over 100GB, it cannot natively run on PSP hardware or even most mobile emulators without significant modifications.
was never officially released for the PSP . Most "GTA 5 CSO" files found online are actually: GTA: Liberty City Stories or mods that have been reskinned to look like GTA 5.