If you see a website offering a "Sims 4 ISO" for PSP, it is likely one of two things:
A "mod" of The Sims 2 Pets or The Sims 2 Castaway that has been re-skinned with Sims 4-style menus and music.
Even though you can’t play the fourth installment, the PSP actually has some of the most unique Sims games ever made. If you have a PSP ISO loader or an emulator, these are the games you should actually be looking for: 1. The Sims 2 (PSP Version)
Don't get discouraged by the lack of an official Sims 4 port. The PSP library offers "strange" and "story-driven" Sims games that many fans actually prefer over the modern versions. Stick to the official PSP releases to ensure your device stays safe from malware.
You must use your own legal backups of The Sims 2 or Castaway .