In this context, .pup stands for . Official files are named with prefixes like PSP , PS3 , or PSV (for PS Vita). For example:
The official Sony firmware updater blocks downgrades. If you want to downgrade to 3.60 (for permanent custom firmware), you need a homebrew app like modoru , and you must still obtain a legitimate PSVUPDAT.PUP for the target version. Psvupdat.pup Download