First and foremost, was developed for the PlayStation 4 and PlayStation 5. It was never released for the PlayStation Portable (PSP). Therefore, no emulator, including the excellent PPSSPP, can run the original Ragnarok files.
The only way to play the actual God of War Ragnarök on a mobile device is through or Cloud Gaming : First and foremost, was developed for the PlayStation
Updated Combat: Some mods adjust the camera angle and weapon textures to include the Leviathan Axe and Blades of Chaos. First and foremost