Is the sale valid and the condition permissible, and is there any Sharia violation in this, and does the ruling change if harm befalls the owner of the showroom who stipulated that the car not be shipped outside America for 6 months, and it was shipped before that period by selling it to a relative who then shipped it?

There is no harm in selling the car and transferring its ownership before the stipulated period expires, because the condition was made after the contract was concluded and became binding, and it was not made during the session of the contract. Furthermore, there was no mention of an option clause (khiyar al-shart) to be attached to the contract. Therefore, the sale is valid and the condition is void.