CBSE 12th

Hello,
Kindly go through this link:
https://www.shiksha.com/mba/resources/iim-call-predictor
Good luck.

There are lots of courses after graduation:
Sales and Marketing
Management
CS/ CA/ CFA/CWA
Computer Courses: MCA/Animation/Web Design
Mass Communication And Journalism/Advertising
Hotel Management
Travel and Tourism
Civil Aviation: Air Hostess/ Commercial Pilot
Social Work
Law
Banking & Finance
Library Science
Teaching: B.Ed
Designing(Garment/Jewellery/Foot Wear/Interior designer)
Content/Technical Content Writing
BPO/KPO
Entrepreneurship
MBA Courses
Animation Courses
Banking and Finance Courses
Computer Courses

Most of the colleges have eliminated the GD process and replaced it with WAT(Written Ability Test) which is more of a test of your thought formation and english writing skill and not just about having the highest voice in a fish-market. But PI still remains the most integral part of the process. Hence if you feel that you are not confident enough in English, I would suggest you work hard towards it and if required join a coaching center for the same and overcome your hurdle.

No, it's not necessary.

It's like an ocean. You have plenty of option to choose over. Every human being born has a goal in life. Sit back and think over what you want to be in your future. In order work along towards it. You can choose course just like that, you need some dedication and passion. So request you to decide on what you want to study.

No, it will never affect your future. If you do well in your B.Tech then it will not affect your future at all.