Reverting to an older software version is called downgrading. Here is a comprehensive look at the technical reality, the methods available, and the risks involved in trying to downgrade a PS4 from 10.50 to 9.00. The Short Answer: Is It Possible?
Do you know the your PS4 was on right before it updated to 10.50? ps4 downgrade 10.50 to 9.00
Download a 9.00 PUP file, put it on a FAT32 USB, boot into Safe Mode (Option 3 or 6). Reality: The PS4 will verify the update package signature and compare it to the minimum version stored in Syscon. It will display: "The update file is older than the current system software" (Error CE-34788-0). The process stops immediately. Reverting to an older software version is called downgrading