IIM

Yes, you can do MBA in any stream that you want. There is no disadvantage, as you are doing it after B.Sc. And yes, you are eligible for IIMS also. For that, perform well in CAT exam.

Not much. You need to ensure that you score a minimum of 50% marks at the graduation level. Admissions in IIM are based on your performance in admission open test CAT and Personal Interview (PI).

IIM offer post graduation courses so you first need to pursue your graduation and ensure that you score minimum 50% marks and then compete in CAT entrance test) and try to achieve a score of more than 98 percentile to get a call for Personal Interview (PI). On successful clearance of it, you will get admission. Offlate IIM Indore also offers an integrated course of BBA & MBA. You can check on their website on the admission requirements.

Yes, you can get call from IIM, but for that you need to give CAT in November and in CAT, you need to achieve more than 99 percentile and then only you have chance to get a call from IIM.

Your 10th marks are good. Your 12th marks are on the lower side. Your UG CGPA is also average. Any non-
managerial work-ex, specifically IT is not relevant work-ex for MBA. You will get some points for your work-ex however. Anyways, if you are a General Engineer, you will need to target 99.9+ percentile in CAT. Also, don't restrict your options to just IIMs. There are some amazing non-IIM Schools also in India that you could apply to - FMS, MDI, IMTG, SP Jain, XLRI, XIMB, JBIMS, NITIE, IIFT NMIMS, SIBM, etc.

As far as I know, CA exam is much more competitive and tough than CAT. Nevertheless, you may wish to complete your CA certification and later on apply for MBA, many students do take that path.

Yes, you are eligible for admission in IIMs. Eligibility criteria for IIMs admission is -
The candidate must possess a Bachelors Degree with at least 50% marks or equivalent CGPA (45% for SC, ST and PWD/DA category). Check the below link for more information-
https://www.google.co.in/amp/s/www.shiksha.com/mba/exams/amp/cat.

According to the IIM admission criteria, candidates appearing for CAT 2017 must have a Bachelor's Degree with at least 50 per cent marks (for General category) and 45 Percent (for SC, ST and PWD category) or equivalent CGPA from any recognised university. The minimum CAT percentile one needs to get a call from IIMs is 93 percentile. The percentile includes the marks scores in 10th, 12th, graduation, work experience, gender, etc.

For admission into any MBA college, they will check your graduation marks. Most of the college keep minimum 60% criteria.