hi pulak, you will need migration certificate only if you transfer to other colleges.i shall tell you more about AIIMS, All India Institute of Medical sciences will be conducting their exam on MAY 27TH 2018 and online registration starts from february 2018. it is a single gate way for admission across all AIIMS in country. the pattern will be as follows

PHYSICS-60 QUESTIONS

CHEMISTRY-60 QUESTIONS

BIOLOGY -60 QUESTIONS

GENERAL KNOWLEDGE AND CURRENT AFFAIRS-20 QUESTIONS

Please do note that there would be negative marks and also make sure that you prepare well for Assertion and reasoning type of questions. hope this helps. good luck