Hello Aspirant, The Exam pattern of JEE Advanced (for IIT) and for B.SC Entrance Exam of BHU are both are different, so if you think you are fit are for JEE Advanced then you can drop for a year for IIT JEE, as it not a easy exam.More over if you somehow enters IIT you don't have have tension of placement as their placements are very good.But you should at least see pattern of IIT JEE that whether you are fit for Exam or not.