I secure 85 percentile in mains and I belongs to ewg,would it be beneficial to give advance.

Yes you should surely go for advance examination.
But you have to surely work really hard.
As there is quite less time left for exams, so it's better to plan accordingly and work hard for exams. You can surely get a good college.
As per your mains results, it's difficult to get a hood college.
So it's better to study hard for advance.

I hope it will help you out.
All the best.