MBA/PGDM

Yes, you need to go for GD/PI rounds. You will also have to appear for written ability test for 15 minutes from this year’s notifications as per JBIMS which is also accepting CAT score.

MAT is not acceptable at IIM Ahmedabad, only CAT is acceptable.
https://www.shiksha.com/Indian-Institute-Of-Management-Ahmedabad-Iim-A-courses-offered-details-institute-college-listingcoursetab-307

SP Jain, ISB Hyderabad, XLRI Jamshedpur, FMS Delhi, IIFT Delhi, MDI Gurgaon, IMI Delhi, IMT Ghaziabad, IIT Delhi, JBIMS, Sydenham, KJ Somaiya, NMIMS, Welingkar’s are top best B-schools.

MBA is post-graduation which means can only be done after having valid graduation degree and not simultaneously, start preparing now in case you wish for MBA.

Hi,
Follow the given below link for the same:
http://www.forbes.com/international-business-schools/#2f65756668f8

Cutoffs, eligibility and admission details of top government colleges in India are given below:
http://blog.oureducation.in/rankwise-best-government-mba-colleges-india-fee-structure/

Yes MBA in systems or MBA in operations are very relevant streams in MBA for engineering graduates. Management gives you exposure to management roles with technical knowledge.

Hi,
You can go for MBA once you complete your graduation, there shall be no difficulty. Start preparing from final year of graduation to appear for the entrances of MBA.
Top colleges have been mentioned in the given below link:
https://www.shiksha.com/mba/ranking/top-mba-colleges-india/2-2-0-0-0

You must choose your MBA specialization based on your personality traits and interests. As a science student, if you are good at numbers then finance can be a good MBA specialization for you. If you are extrovert with good communication and leadership skills, marketing can be a good option.