Because there is no official ISO, the "Resident Evil 4" content you find for PPSSPP is typically a fan-made mod of another PSP game (often using assets from games like Syphon Filter ) or a compressed version of the Resident Evil 4: Mobile Edition
If you are looking to experience Leon S. Kennedy’s mission on a handheld device, here is a comprehensive guide to your actual options and how to navigate the "PPSSPP" community versions. The Truth About Resident Evil 4 on PPSSPP Download Resident Evil 4 Ppsspp Iso