Hey ,BHU takes entrance tests for B.SC, B.COM , B.A and there forms are filled online in mid February via online mode. Then after clearing the intrance a minimum 50% marks needed in 10+2 for admission. Other than these courses for IIT you have to clear Joint Entrance Examination ( JEE ) and for IMS you have toh clear NEET. 

Hope it helps.

All the best for future!!