Exam

Your graduation score is poor but if your 10th and 12th marks are good then you must aim for 98 percentile score to seek admission in IIMs.

At least below 12000 rank is required to get admission into an NIT.

Kindly mention your category (eg. general, ST and Sc) for a better guidance.

Yes, many premiere B-Schools offering MBA in IB do take admissions based on CAT scores, you can also prepare for IIFT, which takes separate exam for admissions.

You can start with reading newspapers daily so that your knowledge on current events gets brushed up. Keep reading GK books and refer to previous year's question papers. Think about your optional subject and prepare for them. For graduation also, take that subject so that it helps in your preparatio

Entrance exams are mainly there to check your awareness about the current events, English language, and logistic aptitudes. So get yourself registered with some coaching centre and get yourself prepared.

Serious preparation is fine in the last year of B.Sc. But you should keep reading books for UPSC exam and brush up your general awareness on current events and GK. Continue with light early preparation as well.

Yes, you get direct admission.

You need a minimum of 600/800 in GMAT.

I don't think you'll get any good college but you can wait for JOSAA and try your luck.