That’s not true. FSD, the purchase, does transfer with the vehicle when sold. (During beta, sure, the new owner will have to enroll, but the FSD purchase is part of the vehicle's resale value now)
So my understanding is that the FSD is linked to the car + user account. If either change, the FSD goes. I guess you could hand over the user account, but i believe both need to go together? Is there a clear answer from Tesla somewhere on this?
FSD gets unenrolled. But the new car owner can re-enroll for no cost, just clicking through some warning screens telling you to pay attention.
if you upgrade your car, you lose fsd beta also, even if you pay for FSD again.
You won't have to pay for FSD again. Stop talking nonsense. And what do you mean, 'upgrade your car'? Specifically? I am not aware of any actions that remove a previously paid FSD entitlement from a Tesla.