Well hold up there....
The RNS-315 is easy to distinguish.....it has the smaller display & then the knob in the middle of the bottom (three knobs across the bottom in total), but it has Navigation. They should all have a camera input btw:
There's the RCD-510, which has a bigger screen but no Navigation. And the early ones didn't have a camera input.
Then there were newer versions of the RCD-510, which could accept a OEM camera input. You can only tell if it has it by pulling it out & looking for the yellow input on the back side:
RNS-510 had the big screen AND Navigation and camera input, but was super slow to run.
Then there's the (Chinese?) RCD-330 which can add Apple CarPlay. I'm not sure about the back up camera situation though and all that.
But anyways....if it has that port, buy a camera w/harness and then hook it up & run the wiring!