The original Resident Evil 4 (2005) runs beautifully on high-end Android devices via Dolphin.
Some modders have created Resident Evil 4 fan demos for PSP using the Silent Hill: Shattered Memories engine or custom Lua scripts. These are: The original Resident Evil 4 (2005) runs beautifully
Searching for "RE4 Remake PSP" will lead you to YouTube clickbait with fake download links. Searching for "RE4 Remake PSP" will lead you
As noted, RE4 never hit PSP. However, Revelations (originally 3DS) has a PSP port – only in Japanese. An English patch exists, but it's a very different game (episodic, ship setting, dodge mechanic). RE4 never hit PSP. However
Your search term includes "APK mod" and "PPSSPP," which refer to two different ways of playing games on Android.