CAT

The CAT cut-offs for admissions are subject to change each year according to the number of applications and seats from year to year. However, if you are above 80 percentile there are fair chances.
Below that chances are very low.

You will get one month after the results are declared.

CAT examination is conducted once a year in November end or December beginning every year.

Each of the coaching centers has the capability to enhance your confidence for CAT and frankly speaking, all depends on your enthusiasm on how you want to manage your studies. Coaching is just a part of your preparation which will take you to the level of competition. As you are confused with your options, I personally would like to suggest you to go for TIME because their All India mocks are the key to cope up in a better way for your preparation. So, TIME would be the recommendable suggestion for you.

You can appear for this exam even if you are in the final year of your graduation.

Your past academic scores do not matter for admission to FMS. As long as you are going to complete your graduation in time, you can always apply for CAT and seek admission to FMS through the regular admission procedure.

TIME institute is best to prepare for CAT exam.

The cutoff for general category is around 97 percentile in the entrance exam. For previous year cutoffs, you can visit DTE website.

You can either join a good coaching institute or you can start self-preparation. You should start practicing the problems. You can also refer to some good reference books for CAT like Arun Sharma.

The coaching classes will certainly help you because you will get to know the format of the exam.
All the best.