Resident Evil 4 was never officially released for PSP. However, you can play the PSP version of Resident Evil: The 4th Player (a fan-made demake/mod) or, more commonly, people install the official PS2/GameCube version using other emulators (AetherSX2 or Dolphin). But — if you're looking specifically for a PSP-style Resident Evil 4 experience, here's the real method to run a playable RE4 on PPSSPP:
It is a common misconception that there is a Resident Evil 4 ROM for PPSSPP. The PSP system never received a Resident Evil entry during its lifespan. When you see gameplay of "RE4 on PPSSPP," it is typically one of two things: resident evil 4 ppsspp android install
It is important to distinguish that the PSP version is identical to the PlayStation 2 or GameCube versions. Key differences include: Resident Evil 4 was never officially released for PSP