You can typically only revert to the previous version that was installed on your specific console. You cannot jump back to an arbitrary version (like 9.00) unless that was the version immediately preceding your current update. Essential Downgrade Tools & Hardware
The PS4 motherboard contains two separate firmware slots: an (current version) and an inactive slot (the previous version). When you update your console, the new firmware is installed to the inactive slot, which then becomes active. downgrade tool ps4
Required for the precision soldering needed to connect wires to the chips. You can typically only revert to the previous
By accessing and patching the console's internal NOR and Syscon chips, tech-savvy users can force the console to switch back to the inactive slot. downgrade tool ps4