Nihal, AIIMS will conduct admission for all its MBBS seats through NEET score. This has been official. Now AIIMS offers many courses like MBBS, PG, B.Sc Nursing, etc. So the basic registration might be for any of those courses. If you go to the official website of AIIMS, it doesn't have any Basic registration process for AIIMS MBBS. Admissions to AIIMS MBBS seats will be done through All India Counselling conducted by the DGHS on behalf of the NMC.