To test the sensor, put it in reverse with ignition on, put your ear next to the sensor on the bumper if you can her it clicking its working. If not its not.
If its not working try warming it with a hair dryer, if any water has got in it will dry it out.
It did on this
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As for having the standard beep when in reverse and then the extra beep with sensors, it seems bonkers to me - I would have one disconnected.
As far the light, I also think the wire to the parcel shelf light will have been re routed to the spoiler.
You just need to split it and connect it back up.
Although when I had mine it was very bright at the back with all the brake lights on so I disconnected the spoiler light rather than the parcel shelf one.