IIM Process

IIM considers 10th, 12th and graduation marks for shortlisting candidates for GDPI round in addition to CAT score. Therefore, if your marks are poor because of history of arrears, it will impact your chances for getting a call. Also, it will create a bad impression in PI round with interviewing board and reduce your chances of selection.

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).

Work experience is seen as a positive for any MBA program in general. You are advised to prepare well on your work experience and learnings and use it to your advantage during interviews. JEE in public sector is a good experience. So, be confident when you describe it to interviewers.

Hi,
If you have increased your grades in graduation. There is no issue, if you have knowledge, skills, understanding, IQ level and you perform extremely well in CAT exam.
All the best.

Yes, non-managerial work experience is also considered in IIMs recruitment. Many technical engineers working in IT companies get admission in IIMs.

Dear Prashant,
Yes, they will give admission to a fresher but preference will be given to experienced people. Until and unless, you get a good score in CAT.
All the best.

If you score 99 to 100 percentile in CAT, you will surely get a call but most of the IIMs require good educational background. You can try for other IIMs if you not getting call from IIM A, B, C.

You don't have to refer to any specific book and not being fluent in English is also fine. All you need to do is be aware of current affairs. Apart from that, you need to have certain skills for a GD, like being a good listener, being assertive and not aggressive, being polite, giving everyone a chance to speak, making sure you are the one in first 2-3 speakers in the group, etc.
If you are not still confident, I suggest you join GD-PI classes of any Institute like TIME. They will teach you well and do multiple mock GDs to boost your confidence.