To downgrade a PS4 from firmware to 9.00 is technically possible but practically prohibitive for 99% of users. It requires micro-soldering, hardware programmers, advanced hex editing, and accepts a 40-60% chance of turning your console into a paperweight.
Elias watched the power light pulse. This was the moment of truth. In the modding community, this was the "suicide drill." The console was effectively lobotomizing itself. It was wiping its secure kernel, trusting the USB stick to replace it with code that was two years out of date. ps4 downgrade 13.02 to 9.00
You can only revert to the version you were on immediately before updating to 13.02. To downgrade a PS4 from firmware to 9