IIM Ahmedabad - Indian Institute of Management

Yes you can. As long as you are eligible as per the X,XII marks criteria (average &get;80 for Science, &get;77 for commerce, &get;75 for arts background), you won’t be directly ineligible for IIMA.
But since your score is less in graduation, you need to compensate for the same by getting a higher per

3 core.

The new fee structure would be implemented from the next batch of 2015-17, IIM-A Director Ashish Nanda said. "For PGP and PGP-ABM, which are both two-year courses, the fee will increase from Rs.16.6 lakhto Rs.18.5 lakh.

For enhancing you Vocabulary go for Word Power Made Easy by Norman Lewis
It is brilliant book that helps you build a strong vocab. I would suggest you to buy this book and keep reading it again.
The book does not forces you to memorize any word, it explains the origin and history behind the word and

There are usually two ways, by taking CAT and then WAT/PI. For second one, if you have lived outside India for at least 18 months and are away during CAT examinations, you can apply to IIMA using your GMAT Score. There is separate process for that.

I would suggest that you write a mock CAT to figure out your strengths and weak areas. Depending on your score you can figure out when to start preparing. Its possible to score well in CAT by preparing rigorously for 4-5 months if your basics are good.
Know more about CAT at :
https://edudrona.com/com

You can opt for one specialization at a time. However you can choose to major in another area as well. Also there are people who do multiple MBAs to specialize in multiple fields.