MBA Eligibility

Yes, you can surely apply for an IIM even you have rejected a previous offer. There are people who do get selected in newer IIMs but they apply again to get into top IIMs. The shortlists are based on CAT score and profile and the number of attempts are not considered. Normally, during the interview process as well, the interviewers do not ask about whether you were selected last time. If they do, then you can give a valid reason for your choice and make them understand the opportunity cost of your decision. If you wanted to have work experience before joining IIM, then you can justify your choice. Having said that, you should really think beforehand whether you want to join or not. There is no guarantee that you will get a call this time if you get it before as it's all relative to the quality of candidates and CAT score.

Well, CV doesn't have points, it always carries weight. How strong your CV is and how capable you are. The most important thing which will be considered during your placements is your CGPA. Companies will shortlist mostly on the basis of CGPA. There have been times when the list of shortlisted candidates for some of the best firms consisted top 10-20 rank holders of the college (literally). So, no matter what anyone says, CGPA shouldn't be neglected. Especially for high demand jobs like investment banking, CGPA is a deciding factor.
After CGPA, they will check for relevant internships. So, make sure that you do at least one or two internships in relevant fields in good companies so that you don't look like a novice. Then they see the past academic records and awards and honours including scholarships and fellowships.
So, the order of importance would be:
1. CGPA
2. Relevant internships in reputed companies
3. Awards and Honors
Don't think that extra-curricular activities matter a lot. It is good to have some to show that you are an interesting person. It may have a bit importance in marketing but not at all in finance. Having important position of responsibilities like the president of the student council or something may be helpful.
But don't neglect academics for that.