BBA

You can get through with some private colleges and through distance education. I would suggest you to inquire from some colleges and to get started, I am listing names which you should look for:
1) IILM at Gurgaon - http://college.iilm.edu/
2) IILM at Delhi - http://ubs.iilm.edu/

Yes, you can do it. Eligibility is only 55% in graduation.

There are lot of colleges for BBA and I would suggest for IILM which have branches in Gurgaon and Delhi which have some unique programs which lets students study abroad and get international exposure. Also, they have some BBA programs for family business, entrepreneurs which makes this college much

Eligibility Of the Master of Business Administration [MBA] (Biotechnology)
A person who is a graduate in the field of medicine or engineering is eligible for this course. Although a person with some work experience (at least 24 months) with research in this field are always more preferable.
How to Ge

There is no option of BBA+ MBA integration after 12th board. It just offers a liberal studies and in 3rd year you have an option of choosing your major and minors according to your choice . The course is for 4 years.

Hi,
You can refer the below link for institutes are offering BBA/BBM in Kolkata:
https://www.shiksha.com/bba/colleges/bba-colleges-india?uaf[]=location&ts=21070284&rf=filters&ct[]=130

As there are no shop which are selling previous year paper so for preparation of BBA you can contact Jamia Maktaba.