If your goal is to play older versions of specific games (rather than the system firmware), you can use tools like RewindPS4 on GitHub . This proxy tool allows you to: Intercept download requests from your console.

: You can only revert to the version you were on immediately before your current one. If you updated directly from 9.00 to 13.02, a revert could work. If you updated from 12.50 to 13.02, you would only be able to revert to 12.50. Alternatives and Status Firmware 9.00

While a traditional software downgrade doesn't exist, a hardware-based "revert" is possible if you have moderate soldering skills.

: Public software-based exploits currently support firmware up to

If you are looking to downgrade a PS4 from a modern firmware to a legacy one, here is the technical reality, the specific risks involving error codes like SU-42118-6, and why the "USB method" is widely misunderstood.