Since you cannot trust anything on that unit anymore, I would recommend to do the following:
Connect the unit to your car using the adapter you got. All the RNS-E are basically connected the same way, at least consistant enough for the next step.
Take your VAG-COM cable and check STG 56. It will tell you the part number of your unit. If it's not a 8E0 035 192C then it's not even the right top cover as shown in your pictures. If it's a 8E0 035 192C then you have an A4 unit and all what's missing is the right faceplate.
Next look at the back of the faceplate. There might be something which says A6 on the left or right back side of the faceplate. We had once someone on the Yahoo forum who got a spare A3 faceplate and it had A3 shown on the back of the faceplate.
You are in a bad position because the A4 unit will not work in an A6. The A4 unit requires speed over CAN which is not the case in the A6.
As next step I would recommend to go into engineering mode and read the serial number off the unit. I would carefully research if this is a stolen device. This may give you some additional arguments when you get back to the seller to get your money back.
Thanks for that.
I'm certainly going back to the seller about this. Not sure how much good thats going to do me. This was handled by a friend who bought the unit while on holiday in Poland for me.
I asked the question here before about model numbers and the differences. I'm confident that once the unit is "coded for the faceplate" that it will take "speed over CAN" or "Speed over Gala" as needed.
Once last comment: You cannot code an A4 unit to take speed from the v-wire, the pin in not connected in an A4 unit. You can however code an A6 unit to use speed over CAN. This is probably what happend to your A4 faceplate which now sits happily on an A6 unit which is coded for an A4...