CAT

It's better if you choose job in that sector in which you want to go after completing your MBA. Talking about if it is really going to affect you or not, it totally depends on how you are managing your studies and job.

Hi,
You can start preparing from right now. It's better to join a reputed coaching institute. But, as you have almost 2 years to give CAT 2018, start with self-study and go through all the basic and after knowing about your strength and weakness in different areas join a good coaching institute. This would ease your preparation a lot. Be like the tortoise from the motivating story "The Tortoise & Hare". Have the zeal like the tortoise and succeed.
All the best!

The cut-off for IBS Mumbai is 70+. Yes they accept all these exams and there scores.

Yes, you can go for a drop year, but in MBA during internship and interviews reason for drop years will be asked.

IMO, TIME is better. Their study material (both online & classroom) is quite exhaustive. Also, I've heard their mocks are at par with the actual CAT. If possible, you can attend a demo lecture of both these classes to get a better idea.

Hi,
Try the given below link;
http://blog.oureducation.in/top-10-cat-coaching-centers-patna/
I hope it will help you.

Yes, you can appear next year for CAT. But during internship and placement, interview questions will be asked about your gap in education. So prepare a good answer for that. Investing one more year with proper planning for preparation will improve your score and will help you to get into top B-Schools.

The cutoff goes to around 85+ every year, with minute fluctuations.
LBSIM has no reservations on the basis of caste.-Samant S. P.
Official, LBSIM

It is possible to appear for CAT exam but you need some eligibility, you should clear your Bachelors degree with minimum 50% and the certificate should be from any university that is accredited by ministry of HRD, government of India.