Best option to for KVPY!

Research needs high dedication and major experience and for that you start as your interest after 12th but you need to alteast complete your PG after that you can go in research completely.

To become a scientist you must give the following level of exams.
Some of the institute conduct the own entrance test like:
BARC
IISc
TIFR
Common entrance test jointly conducted by 23 research institutes in Physics, Chemistry and computer science that is JEST

You can also fight for the CSIR NET Exam. After qualifying this exam you can work under the top 32 research labs in India, under the top scientist of INDIA.

Hope this helps.
Good Luck!