hi,

see you can appear in kvpy exam in 12th class, when you are in final year  of 10+2 course. there is no need to mention your 11 th percentage, but question will come from 11th and 12th syllabus both. so you need to study strictly for both of the exam.

follow the previous years question, and if you are preparing for jee main exam or neet exam, it is an added advantage for you.

all the best for your future.