I believe you can order upgrades post purchase like FSD/acceleration boost, etc and have 48 hours to get a refund. After that you can purchase it again but then no opportunity for refund. I do not know how it works though if your purchase FSD before taking delivery of the car.I was under the impression that once FSD was unlocked it was permanently tied to the vehicle and couldn't be turned off? So if you canceled, you'd have to change to another car and that may impact your delivery date?