:

The only legitimate method that resembles a "tool" involves hardware-level programming. This requires:

I understand you're looking for information on PS4 "downgrade tools." I need to be upfront with you:

The downgrade tool worked by injecting a custom payload into the PS4's memory, which then allowed the user to rewrite the console's firmware to an earlier version. This process was not without risks, as it could potentially brick the console or cause other problems.