If you want to play Resident Evil 4 on your Android device, you should use emulators for systems that actually hosted the game, such as the GameCube or PlayStation 2. Recommended Way to Play on Android To get the best experience, use the Dolphin Emulator (for the GameCube version) or AetherSX2/NetherSX2 (for the PS2 version).
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: resident evil 4 ppsspp android install