You must solder wires directly to the tiny pins of the PS4's NOR flash chip and the Syscon chip.
Even this advanced method has massive hurdles when dealing with version 13.02: ps4 downgrade 13.02 to 9.00
To go all the way back to 9.00 from 13.02, your console must have sat on firmware 9.00 immediately before you updated to 13.02, without any intermediate updates (like 10.00, 11.00, or 12.00) in between. You must solder wires directly to the tiny
If you are still on firmware 9.00 or lower, you can prepare for the future by backing up your "EAP Key" (Encryptions Key) using a jailbreak tool. However, if you are already on 13.02, it is too late to do this without a hardware flasher. However, if you are already on 13
No. You cannot downgrade a PS4 from firmware 13.02 to 9.00 using a simple USB flash drive or a software-only menu trick.
This process is incredibly complex and dangerous, requiring advanced electronics skills. It is not a software solution.
When you try to install an older firmware using the standard USB method, your PS4 will simply refuse to proceed. This is due to a sophisticated hardware-based security feature.