MBA Entrance Exam

You may refer to following link for all details on CAT 2016 examination: https://iimcat.ac.in/per/g01/pub/756/ASM/WebPortal/1/index.html?756@@1@@1

Both have different formats of studying. For CAT, you need to focus on data interpretation, logical reasoning and verbal aptitude with as much as mock exams you can give.
For TOEFL, you need to focus and practice your speaking and hearing skills and need to be well versed with words and synonyms.

Yes, you can apply with December MAT score.

February MAT will not be considered for 2017 admissions.
You can apply via XAT score.

You have cleared the cutoff required. So you are eligible for admissions. New cutoffs will be out shortly.

yes you can. all major b schools in India accept GMAT scores. 650 is a good score. minimum cut off for IIMs is 550 .

The results, the admission process will take roughly 4 to 6 months, so your curriculum will start by the end of the year or at the beginning of the next year depending on university to university.