no, there's no way to revert newer firmware to old one unless the hacker implement those feature it's called modoru on psvita, or the hacker find a way to hack ps4 firmware and make them like ps3 cfw
the easier lower budget version of this is to go to the system information get a piece of paper and write 9.00 on it then tape that piece of paper to the screen over the 9.04 number