From what I read the order goes: Tesla employees > Space X employees > Tesla current owners.
Does anyone knows buying a used Tesla would consider in that list or it has to be a new Tesla vehicle?
According to Tesla, it goes by whether you own a Tesla. They said nothing about whether you bought it new or CPO or even from a private party. My understanding is that if the email address you reserved with is in their database as a current owner, which would be the case if you have an active My Tesla account that shows a Tesla of any sort as a current car, then you'd qualify. You'd have to double check with Tesla, but it seems that they would have to go out of their way to cross check that list against other records if they wanted to exclude those who didn't buy the car new, and they'd have to make it clear to current owners.