IIM Ahmedabad - Indian Institute of Management

No, IIMs only provide Diploma in General Management.

85+ percentile will help.

I presume you are asking about DA category cut-offs. To get admitted at IIM A, you need to secure 87 percentile above in DA category.

You need to put some additional effort for VA section. For other sections i would suggest you to go through the basics in couple of months and start practicing questions. In case of VA, the basics of English, tenses, usage can be learnt from basic reading material provided by CAT prep books. After than i would suggest you to practice RC from readtheory.org where you can build you reading comprehension skills with time. After gaining a bare threshold, start giving mocks, analyze them and repeat till the D-Day.
All the best

Assuming you have average acads, you can expect calls from baby IIMs. Calls from new IIMs would be unlikely since you have less than 96.5 percentile.
All the best!

IIM- Ahmedabad do not have a 0 fee admission. Students have to pay the complete course fee to study at IIM-A i.e. Rs 19.5 lakhs for 2016-2018 batch. IIM-A do have scholarships based on academic performance or financial status which subsidizes the course fees to some extent.

Target a CAT score of above 95 percentile if you want to get into top 25 B-schools in India. Usually, IIMs do not provide specialization and give a diploma in General Management. You will get a PGDM/MBA degree from such colleges. While colleges like S.P Jain gives MBA/PGDM with Marketing/Finance/Operations specialization.

Total expense is Rs 10-15 lakhs.

MBA in finance will give you a slight edge over others while grabbing initial concepts. While doing in marketing you will not get any such advantage. Choosing specialization should depend on your interest rather than expertise, because you can gain expertise with time, but your interest remains for long term.

It depends, how do you define normal. It varies from Rs 20,000 for the whole program to Rs 20 lakhs in case of IIM-A. On an average, considering top 25 B-Schools, it would hover around Rs 10-15 lakhs.