The PS4 motherboard contains two "slots" for firmware: one active and one inactive. When you update from 9.00 to 9.60, the system installs 9.60 into the inactive slot and then swaps it to be the active one. The old 9.00 firmware remains in the other slot until the next update overwrites it. Requirements for Downgrading

Versions above 9.00 (including 9.60) currently lack a public, full-kernel exploit.

There is one scenario where downgrading might be possible, but it is expensive and not practical for most users:

How to Revert the PS4 to a Previous Firmware (Full Tutorial)

: While 9.00 was historically the most stable version for exploits, modern jailbreaks (like those utilizing the PPPwn exploit ) work on versions up to 11.00.