Screen does not dim because light on signal is not available in the accord old head unit wiring.
You can get the light on signal from the connector of the old screen. However, it will take lots of effort. Have a read of previously shared article if you want to get the light signal.
regarding reverse camera, you might find following video useful,

 

If you already have factory navigation, it's probably better than any of those aftermarket screens in terms of quality and longevity. I don't see a reason to replace it.

 

Hey Ash, so I finally had some time to do the backup camera and I can't not get it working. I plugged everything but there are two short red wires on both end that are not connected to anything. Do I need to get another wire and connect those two short red wires? Pictures are below.

 

You need to do three things,
1) In the boot of your car, connect both of the red wires to the +ve of reverse light.



2) Find a cable in the harness of new head unit that says something like reverse.

3) Connect red wire shown below to the reverse signal cable identified in step 2.


It should work, if it doesn’t work then you need to verify that you have connected red wire to + of your reverse light wire.

 

those are pretty much the only wires I see that are not connected.

 

Here is what I found on the internet, do you see a pink wire?
if not, share the link to your headunit



I think that it is the pink wire on the following black connector,
you might have to cut this wire and add your red wire to the pink one.
however, ask your head unit supplier about it.

 

Could you elaborate more on the wiring please? Red and Gray is ground I assume and where would I get 8V for the green cable?

 

Send me a closer photo of the following connectors,

 

So I plugged in the red wire to the pink wire on the head unit and I am not getting anything still. I also connected the other red wire at the trunk to the trigger also. Still nothing. So on my reverse brake, there is a black wire and a blue wire. Am I assuming the blue wire is the trigger? So I connect the red wires to it?

 

I think that pink wire in the following photo is the reverse trigger wire. Rev trigger automatically shows reverse camera image in the display when 12v is applied to it.
I tried looking for Android head unit wiring diagrams, all of them are built different.
therefor, this is a guess.
you can contact your supplier for confirmation.
if supplier confirms that pink is the correct wire,
you then connect red wire from camera cable to pink wire.