What is the correct way to wire the backup camera.
There are 4 wires involved. The first two are the camera ground and video signal wires. In your case these two are wired correctly.
The reverse trigger can be wired to the transmission reverse switch (uncommon), to the ECM (not available in all cars) or to the reverse light wiring itself. I believe the installation manual instructs you to do the latter. In any of these cases, when the AVIC picks up a signal on the "Reverse" wire, it switches to the reverse camera input. In your case, this seems to be working.
YOUR PROBLEM:
The last wire is the 12v+ for the camera itself. A lot of installers go the quick and easy route and just tap the reverse light + to get this power. The logic being its a "reverse" camera, rather than a rear view, and would only need power while in reverse. Doing it this way saves them from running a new power line. Unfortunately it means the camera flat out doesn't work if you aren't in reverse.
TO FIX IT:
To wire it correctly, you need a 12v switched power signal to the camera. This would give the camera power anytime the car is on, allowing you to manually view it, while the AVIC would also auto switch to it when in reverse. If you are lucky enough to have daytime running lights that also power the tail lights, its a simple matter of moving the + wire from the reverse light to the tail light. (make sure you get the tail light, and not the brake light) If you don't have full on tail lights, you'll need to find another way to get 12v power to the camera when the car is on, rather than only when it's in reverse.
I can not get the backup camera to display while the car is in park or drive. It works when the car is in reverse. I know about the rearview button in the av source. When I hit it I get the same screen as in reverse but no image. The camera is set to On and Polarity-Batery. I had the unit installed at Bestbuy. Please Let me know what I am doing wrong. Thanks.