As per the eligibility criteria for CA CPT, you should have passed 12th and there is no specific percentage mentioned.

Also candidates who have completed graduation or post graduation in Commerce stream with a minimum of 55% marks in aggregate of all subjects or its equivalent from a state or nationally recognised university are exempted from CA CPT.

So incase you have done bcom and have percentage above 55% you do not need to give the exam.

Rest criteria you can check here for CA CPT entrance. There is no mention for reserved categories.

Good Luck.