Dear Chaitanya,

I am glad to inform you that You are applicable for CAT Exam but at the time of admission you must cleared your backlog first.
It is fine to have a backlog when you are writing the CAT exam. But what is important is that you clear all your papers of your graduation before you enter the college which is generally in the month  of June or July.
Those candidate have completed graduation degree with above 50% marks are applicable for CAT exam but your degree must be recognized.
For SC/ST candidate the percentage is 45 % in graduation.There is no age limitation for the candidate.Final year student are applicable for This exam.

Hope you got your answer.

Good luck :)