IIM

No, the thing that matters is your graduation score and mainly the CAT score.

There are multiple range of topics, nothing is predetermined, you need to be well versed with all topics and current affairs to gain competitive edge over others.

To get admission in IIM for MBA, you need to score more than 98 percentile in CAT exam.
All the best.

Yes, provided you have at least scored 50% marks or more in your 10th, 12th and graduation. Also if selected for the interview rounds, you need to provide them with a valid explanation about those low scores (if asked).
Good luck!

CAT is national-level MBA entrance examination conducted by the IIMs for admission in their MBA program. Admission to IIMs is two stage process. First stage is based on CAT score. Candidates who clear CAT are called for GDPI. Selection is based on CAT score, GDPI performance and academic records. Different weightages are given to these evaluation criteria.
The minimum eligibility criterion for admission in MBA in IIMs is at least a 3-years Bachelor's degree in any subject from a recognised university with at least 50 per cent marks or equivalent (45 per cent for SC/ST or persons with disability (PWD) category).

To get admission in IIMs, you need to score a minimum of 75 percent marks throughout your academics.

The minimum percentage required is 60% for most of the IIMs. But this will not suffice considering you are competing with students with a much higher percentage. The more the better, but it's no guarantee as there are many factors other than 10/12 scores, which are considered by IIMs at the time of selection/ admission.

A management degree is what you pursue from an IIM. Assuming you want to pursue a management degree, IIMs are some of the best institutions in India to do so. Advantages include soft returns such as increased personal reputation to hard returns such as good pay packages. IIMs certainly have advantages over other lesser and newer institutions including a wide network of alumni who are generally supportive. Many points as to the advantages can be made, but the least I can say is that you can be quite sure of them with IIMs.

An UG degree is essential for applying to IIMs for a management degree. If B. Com is the only UG degree you have then it will be considered essential for the admission. So yes, your percentage in B.Com will be a part of the evaluation and it will carry a certain weightage in overall evaluation as well.

Yes, you will be eligible. But, the chances are less. Most top IIMs look for students who have performed well consistently. However, if you perform extremely well in CAT then the chances of getting interview call are higher.