There is no rule that if you have completed your MBBS through AIIMS, you cannot take up NEET PG and vice versa. Even if you have completed your MBBS in any other Medical College and you want to appear for AIIMS PG, provided you meet the eligibility criteria, you can still appear for AIIMS PG. You can check the eligibility criteria at: https://medicine.careers360.com/articles/aiims-pg-eligibility-criteria . The same way if you have completed your MBBS in AIIMS, provided you meet the eligibility criteria for NEET PG, you can appear for NEET PG. You can check the NEET PG eligibility criteria at our page: https://medicine.careers360.com/articles/neet-pg-eligibility-criteria