Hello. Since you have not mentioned clearly which exam you want to appear so I cannot specifically help you with any particular eligibility criteria. But in general you can appear for any Engineering entrance exam if you are appearing for your class 12 boards. But you must fulfill the eligibility criterias for different exams.

Below link will provide you with all the Engineering entrance exams for undergraduate course in India.

https://engineering.careers360.com/exams?page=1&level=1&sort_filter=pop

Hope this helps. Good luck!