Hi, my name is***** your mechanic automotive expert, and I will be happy to assist you today. In some cases, I may need more information to assist better. I apologize for any delay.
Dear customer, I am sorry that you are presenting all these problems, I will try to structure my answer as best as possible:
1) Regarding the rear door on the near side that has stopped working, it is normal for the handle mechanism to come loose, so the ideal is to proceed to disassemble the door upholstery to access the handle mechanism and verify if there is something broken that needs or even replacement of the complete handle or if it just came loose you should tightening it, you will realize that it is not a very complex mechanism.
2) As the handle mechanism is affected in the door, surely the complete lock mechanism on the passenger side has stopped working, therefore it does not activate even with the central locking system and not even with neither of the handles, so the second recommendation is that you also disassemble the door upholstery and check for problems at the door mechanism, surely it could be problems at the lock level and you will have to replace it, but you could save from handle mechanisms and selenoids which are more expensive than lock.
3) Regarding the reverse camera and the radio, I think they are problems at the level of the rear wiring because both are sharing wiring, I think the camera is working correctly, but that the rear connections of the equipment are the problem, surely you can have rust and corrosion, so to start is is good to clean it with electrical contact cleaner, and the if it is not working check the signal and the whole wiring loom.
My goal is to give you the best advice i can based on your description, I hope to be helpful, if you have any doubt please do not hesitate to reply back.
Kind regards, Sebastian.