First go through the NCERT twice make your concepts clear then for other refrence books for more practise.I would suggest you -

1-HC Verma for phyaics

2- RD sharma for maths

3-After reading Chemiatry NCERT its your choice which book you wanna study there are many books for practise.

Also at last practise as much previous year paper as you can .

Hello Mohit, As you are aspiring for the BHU bsc entrance exam as far i know about them is that the question are of the 12th boards level so i suggest you to go through NCERT books of PCM which helps you a lot in the exam. Some of the books that you can go through are

1. H.C.Verma- for Physics

2. NCERT- Specially for Chemistry

3. R.D.Sharma/K.C.Sinha- for Maths

As you hve asked for previous year set then i suggest you to solve atleast 3 to 5 years and atmost as you can as it tells you more about the pattern of the exam so that you can able to know it yourself better to how to prepare for the exam.

Hope you find it acceptable to you.

Good Luck Mohit!!!