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
with rollback you have no input lag on your end, it feels identical to playing offline. if your opponent countered your move before you saw it happen on your end it "rolls back" to that state. eg. lets say you do a jump-in roundhouse you might see them get hit for a split second but then you get dp'd out of the hitting animation cause your opponent actually anti-aired you in that split second you just didn't see it until slightly later when the packets arrived. imo its way better than playing with input latency