PS4 on most recent firmware

Hi,

Noob here in regards to PS4 hacking.

My firmware is on 6. My understanding is that this is not hackable. Is this true?

If that is true, looking online there seems to be ways of completely rebooting PS4 and using a USB to install firmware 5.05. However I am reluctant to believing this is true. Anyone know whether this is true?

Any help would