i plan to give jee in 2014. i am appearing for boards this year if i do not come in top 20 percentile this year can i appear in improvement exam for 1 or 2 subjects and improve my score

NO,IT IS NOT POSSIBLE.IF YOU GET 9O% IN 1ST AND 2ND YEARS IN BOARD EXAMINATIONS,YOU WILL BE ELIGIBLE TO WRITE IIT ENTRANCE EXAM.iF YOU DONT GET 90%IN THE FIRST ATTEMPT YOU WILL WRITE ALL EXAMS IN BETTERMENT.IF YOU GET 90% IN BETTERMENT IT WILL BE ADDED TO YOUR SCORE.1 OR 2 SUBJECTS YOU WILL WRITE  IT WILL NOT ADD WEIGHTAGE TO IIT.