No, it has not to be done everytime.  If You have already completed your basic registration , you don't need to register again.Candidates,those who have filled the basic registration form not need to again re register the basic registration form.

In the final registration form, you have to upload images, signatures, thumb and pay the registration fees. They can be done by log in and fill the final registration form. AIIMS PG application form can be filled through PAAR which includes basic and final registration stages. Also, Once you have completed the Basic registration process and it has been accepted, every time you want to appear for NEET PG, you only need to complete the final registration process and even this applies for July 2020 session. So, you don't need to register again, because your data is already saved in AIIMS PG basic registration form . You have to only fill the final registration form.