A: No. Sony never released it on PSN. Your only legal options are a PS2, PS3 (backward compatible model), or PC emulation (PCSX2).
— What “PKG” means PKG commonly denotes the PlayStation package format used by Sony platforms (notably PS3/PS4/PSP/Vita in various flavors) to install games, updates, or DLC. In modding and piracy scenes, PKG files are used to distribute repackaged games that can install on custom-modified consoles. Important points: gran turismo 4 ps4 pkg top