Here is the breakdown of why this ISO doesn't exist, what files you are actually finding online, and the best alternatives for your PS2.
What do you want to play on? (PC, Steam Deck, Xbox, etc.) Do you need help with performance mods for the PC version?
If you are searching for this file, you need to know the technical reality behind this long-running internet myth, why a functional PlayStation 2 version of GTA 4 does not exist, and what your actual alternatives are for playing the game today. The Technical Reality: Why GTA 4 on PS2 is Impossible