The PS4 motherboard stores firmware data in two separate "slots": an active slot (current version) and an inactive slot (previous version). When you update, the console flips these slots. : You can only revert back one step .
Directly downgrading a Go to product viewer dialog for this item.
However, a hardware-based "reversion" technique exists that allows users to switch back to the previously installed on that specific console. The Reversion Method: How It Works
This is a highly technical process that requires opening the console and performing precision soldering. Essential tools often cited in guides like ConsoleMods Wiki include: Firmware Revert - ConsoleMods Wiki