How to Downgrade PS4 from 10.01 to 9.00 Tutorial + Download - YouTube
PS4 Jailbreak | Downgrade/Revert process explained - YouTube
It is apparently possible to revert your PS4 to its previous firmware version, without any backup - Wololo.net
Scena PS4] Un nuovo video tutorial spiega come eseguire il ripristino della console PlayStation 4 ad un precedente stato di jailbreak – BiteYourConsole
How to downgrade PS4 9.50 Beta software to the previous version of the system software - YouTube