Hey Shreyansh.

I am sorry to I form you but you cannot appear for IIT JEE Mains 2018. First of all you you will have to clear your compartment this year to appear in it. Only then will you be able to appear for it. You should have appeared for compartment examination in mathematics in 2017 itself.

If you had had only improvement examinations to take, then you would have been eligible provided you get 75% in your overall board exams.

All the best.