Yes but it's better to own the device so you can flash the stock tune any time you want and i read some car updates will miss with the tune so if you have the device you will just flash your tune back instead of going back to the tuner
its the same thing you buy the device once + 4 credits to tune the mustang
if in the future you got a new car or whatever you just buy credits to tune or even you can sell the device if you don't want to use it anymore
here read this article it explains the credits
https://www.hptuners.com/articles/how-hp-tuners-credit-and-licensing-system-works/
And i think you need 4 credits for a mustang
mine had paint chips in few places but they showed me all of it before selling the car to me and gave me discount + touch paint for the areas affected and free roof peelable paint for the roof and Wing
The gt performance package rear is 27.7" diameter 275-40-19
The 325-30-20 is the same exact diameter 27.7"
For the front i went with 275-35-20 its .6" bigger
i bought mine from alibaba as well custom made and they turned out great and the fitting is perfect its all about from who you buy not everything is a scam