Dear student.

Greetings.

You can do anything you dream of if you stay focused. But, since you are starting too late you will have to word really hard as the students who prepare for 2 whole years also have trouble scoring a score so high. My suggestion is that you stick to your NCERT books and prepare so good that you are able to solve any question from your NCERT book,be it solved example or exercise. IF you are able to do this, then you will surely clear JEE main examination, even if you are unable to score above 200. 

Thank you. All the best.

it dependson your ability .. your knowledgr and yes hardwork also .. your are in 12 that means you have studied 11 and almost 12 and syllabus of jee is also same .. so yes you can start and if have a ability to do so you can follow strict schedule of regular study and opting not so many books take 1 or 2 books like SC Verma for physics and you can also  take help from teachers to clear your doubts .