Um, your first translation is wrong, the third's a bit over simplified.
The first one says that DSC is NOT working on this car. (Literally says "not yet developed")
VORSICHTIG FAHREN = DRIVE CAREFULLY
Middle, you are correct.
Right one, you are missing the real message:
Airbag Activated - With the laptop installed do not use the passenger seat or put anything on it.
Presumably because if the airbag deployed, the passenger would wind up with a laptop in his face.
I posted this picture along with a few others in another
thread. This is an E90 test vehicle that has a laptop computer and datalogging hardware mounted in the passenger's seat area.