The short answer is . It is technologically impossible to run the official, unmodified version of Forza Horizon 4 on the PPSSPP emulator. 1. Platform Exclusivity
If you want to play the actual game, it is available on: Forza Horizon 4 Ppsspp
Vehicle skins are swapped out to include iconic Forza cover cars, like the McLaren Senna. The short answer is