You cannot simply "install" an older firmware version from a USB drive on a PS4. Sony's security prevents any software-only downgrade to protect against jailbreaking.
Since you can't go back to 9.00, the next best option is to by jailbreaking it. The good news is that firmware 9.60 has been fully exploited and is compatible with a stable jailbreak. how to downgrade ps4 9.60 to 9.00
You cannot simply "install" an older firmware version from a USB drive on a PS4. Sony's security prevents any software-only downgrade to protect against jailbreaking.
Since you can't go back to 9.00, the next best option is to by jailbreaking it. The good news is that firmware 9.60 has been fully exploited and is compatible with a stable jailbreak.