About Trailer coupling and licence plate: which statement is WRONG?
A light trailer (up to 750 kg) gets a yellow plate with its own registration; a heavy trailer (above 750 kg) gets a white plate with the car's registration.
Trailers with a breakaway braking device may NOT also have an auxiliary coupling; the two work in opposite ways (book p.231) and combining them is a defect, not extra safety.
The same up-to-750-kg rule applies to bike carriers that hide the car's licence plate from view.
The choice (breakaway device OR auxiliary coupling) only applies up to 1,500 kg; above 1,500 kg a breakaway braking device is mandatory and an auxiliary coupling alone does not suffice.
Explanation
Book p.231 - it is exactly the reverse. Up to 750 kg: white plate with the towing car's registration. Above 750 kg: own registration certificate with a yellow plate and its own registration number.