I have a 2006 Audi A4 B7 Avant 3.0TDI. It has front and rear parking sensors, but one of my front sensor is malfunctioning (randomly beeps when I'm parking). I think it's one of my sensor near the grille, built in the mask (it was already replaced by the previous owner in the past).
So my question is: Are rear and front sensors the same? If I'd buy a used one (rear or front), can I replace my faulty one?
I red somewhere that even the front sensors are different (2 in the mask grille, 2 is at the outer side have different angle). Is that true? if yes, what are the part numbers for each?
And what about aftermarket sensors? Worth it? As it's only 1 sensor out of 8, I don't want to buy a whole front-rear set of them.

Another problem is with myright side folding mirror. When I fold my mirrors, everything is OK, but when I unfold them, the passenger side mirror doesn't stop and goes out too far.
I can't move it back by force (for the first time i was able to move it back easily, but now it seems it just "ticked" to its place, and I'm not able to move it anymore by hand).
I red somewhere that there is a spring inside the mirror and and a "stop position" , but a mechanic part just jumped over that stop position and that's why the mirror goes out too far. I want to disassemble it and repair/set it back it manually, but I'd need a step-by-step, detailed tutorial for this.

Can you help me in these topics?

Thanks for your help and assistance!