CAT Scores

Experience is not must.At 85 percentile you will get call but conversion is in your hand.

Althought most colleges accept CAT score but there are few very prestigious colleges which have their own exams like Narsee Monjee Mumbai, XLRI etc.
Also taking multiple exams reduces the risk just in case you mess up in CAT. You must register for XAT, SNAP etc.

99+ percentile.

Yes you can. As long as you are eligible as per the X,XII marks criteria (average &get;80 for Science, &get;77 for commerce, &get;75 for arts background), you won't be directly ineligible for IIMA.
But since your score is less in graduation, you need to compensate for the same by getting a higher percentile in CAT. Based on CAT 2015, you will require 99.8+ to be on the safe side for a call from IIMA.
All the Best!

Minimum CAT score required is above 85percentile to get into NIBM.

B.Tech in CSE is in demand these days. You may or may not get it.

Dear ishani priya. yes there is a possibility to get in good government college. apply for the same. and wait. all the best and have a great future.

There is no fixed answer to this. However you are seriously disadvantaged in terms of your percentages. To make up for that you will have to score really well in CAT. In my personal experience you will need at least 99.7 - 99.8 percentile overall. However the criteria to compute composite score changes every year and also the scoring depends on the incoming batch. But in general with 99.7-99.8 percentile you should get more than one call from IIMs.

Some of best institutions of the country accepting CAT/ MAT/ XAT/ CMAT/ GMAT are
1. IIM Ahmadabad/ Bangalore/ Kolkata
2. IBS Hydrabad/ Mohali
3. Lovely Professional University, Punjab
4. NMIMS, Mumbai
5. ISM, Dhanbad
6. Great Lakes Institute, Chennai
7. AIMS, Bangalore
8. Kirloskar Institute, Pune
9. Pune University
10. UPES, Dehradun
Check their websites for more details.
Good luck.