IIM Ahmedabad - Indian Institute of Management Vastrapur Answered Questions

You can start preparing diligently for CAT. If you do not have much idea about CAT, I would suggest you to join a coaching institute with good faculty to help you get the basics right in DILR/Verbal/Quant. After the basics the next challenge is to solve the said question within a stipulated time. Hence, second stage of your preparation should deal with giving mocks and analyzing your mistake repeatedly till CAT.

No MBA in mergers and acquisitions is not offered by IIM Ahmedabad. IIM A only offers degree in general management. Having said that, you can always take electives regarding mergers and acquisition in 2nd year, if you have particular interest in the said topic.

Yes, its worth every penny. The level of faculty, interaction with peer group and learning is unparalleled in India. Hence, its worth it.
Do understand that unlike other government institutes (read IITs/NITs), IIM's do not take any form of monetary support from government. Hence, the complete expense of the education is born by the students itself rather than the tax-payers of India.

It is not something one can answer for you. It's something you need to discover for yourself. Rule of thumb: If you want to stick with the technical line then M.Tech. If you are more interested in management then MBA. Refer to this TOI article to make a more informed decision:
http://timesofindia.indiatimes.com/home/education/news/MBA-vs-MTech/articleshow/21908011.cms

Sorry to inform you this but your BE score will definitely play a spoil sport for admission to IIM A, no matter how high you score in CAT percentile terms. Having said that, I would suggest you to prepare one more year meticulously, to aim for FMS which does not consider previous academics while selecting candidates for admission.

The selection process of all the IIMs is a two-stage process. The first stage is a shortlist based on your CAT score(CAT or the Common Admission Test is an exam conducted by IIM's every year for admission to various courses. CAT scores are used by all the IIM's and many non-IIM's as well) and your academic scores(class 10, 12, under graduation, post graduation etc. Different IIM's set different proportions of CAT score and academic scores to shortlist candidates for the next stage). The next and the final stage consists of Group Discussions and/or Essay Writing tests accompanied by a personal interview. The final selection is made by combining the scores obtained in CAT and the individual components in stage 2.