The T-Rex 4.6 is the updated version of the 4.5, and the only one that the Predasaur security update works on.
Support for this cam is very poor, at the moment, and there isn't even a Predasaur update for the Premiere key change.
To open premiere, on this cam, you need to load Predator 359, as the T-Rex 4.6 can use either predator or Predasaur firmware.