Hey

“Winners are not afraid of losing. But losers are. Failure is part of the process of success. People who avoid failure also avoid success.” - Robert T. Kiyosaki

Dear Ajith
When compared to engineering entrance exams, the board exam will be easy.  You just need to take help from your lectures and they'll guide you to learn and what are the important questions. The important questions only will repeat in every year. Just believe in yourself.  If you don't understand it,  try to practice and try to raise a doubt to teacher.
If you want anything else, comment here.
All the best.

You can still do engineering.All you need is to appear for reexam of 12th.And after that you can give engineering entrance exams.You have work very hard.Concentrate on your basics and clear it from ncert.Now focus only on ncert books.Read it two times...solve numericals.Take guudance from teachers.Solve previous years questions for practice and to enhance your skills.Be confident and calm while going to appear for any exam.
Good luck.