GST Refund for Person with Disability

An Unregistered Person with Disability (PWD) has purchased a vehicle from a car dealer paying GST at the rate of 28% on the vehicle against the concessional rate of 18%. Now he has obtained required certificates from Dept. of Heavy Industries.

1. Can he claim the refund of excess tax paid now under Sec 54?
2. If yes, whether application has to be made to his Jurisdictional GST office or to Jurisdictional GST office of vehicle dealer?