Dear Murari, 

As per the minimum basic eligibility criteria of AIIMS MBBS, you are eligible for appearing in AIIMS MBBS 2019. Coming to NEET, since new brochure and information is yet to be released by NTA, the new examination conducting authority of NEET, we can't say anything for sure. 

Going by the rules which prevailed last year, you need not be worried about the gap between 10 and 12. Upper age limit, on the other hand, can become a concern for you in a year or two when you attain the age of 25 years. But before that, you can appear for both the exams, unless any new changes are announced by NTA for NEET 2019. The clause of gap year was redacted by MCI on Delhi High Court's ruling. We all are hoping that to stay this year in NEET as well. 

Hope it helps. 

All the best!