Hii Mohit! You can definitely apply for CAT in your graduation so as to get a knack of the level of paper set. However, you cannot take admission while your graduation is going on. You can complete your final year and just after that take an admission though

Hello Mohit! The application forms for CAT will release around august or september. It is for post graduation and above programs mainly. You can appear for it in third year of your graduation. Hope this helps.