Hey Parth

As far as I know the concept of domicile in JOSAA is a bit different. Your home state or domicile state will be the one in which your class XII school is situated. You must have typed in your school location while filling your jee form, that address will be considered for domicile hence I will recommend you to select the NIT in Gujarat. Moreover even if your caste certificate is from Rajasthan it does not matter as long as it is valid (the validity date is usually mentioned in the caste certificate itself). Incase of EWS category or OBC NCL category you will have to get it renewed from the near tehsil office (since it is 8 years old and might not be considered now)