Ad 1: Only when car…
Ad 1: Only when car manufacturer proves overspeed was the reason (e.g. car felt appart due to really bad road)
Ad 2: Car manufacturers by my opinion MUST obtain legal ground and it surely cannot be a Legitimate interest or even contract (data not strictly necessary to perform a contract). If there is no law requirement, then explicit consent (which could be withdrawn.
Ad 3: Unfortunately yes. I am driving a Renault which is apparently uncapable to correct bugs in its EasyLink.