HI bro, there will be no problem in april jee mains as you have to again place an another application for it and you have to again write the exam so there would be definetly no problem when you vchange your caste but you should definetly have the caste certificate of OBC which was given by the state government which you have to submmit it through online while applying and which will be verified in accordingly in your councelling , if you dont have at the time of councelling definetly your seat will be cancelled and severe actions will be taken under law so definetly you should have the OBC certificate bro and this certificate also improves your chances of getting a good college and a good branch and this will help you to have a bright future and in many exams also this certificate has its own value , hope you will have a bright future and you will get succeded in your future in qualifying thus exam and all the best for your comming exams bro