Hello Debasish Dey..Firstly congrats for that good percentile.

Percentile= (marks you got*100)/(toppers marks in that session).

According to careers360 rank formula, 

Rank formula= [(100-total score) * (no of students wrote exam)] /100

No of students attended are 874469.

So your expected rank will be nearly around 3,391.

As per previous year jee mains, any rank below 2,00,000 will be qualified for jee advanced.

So according to expected rank of yours, so you are eligible for jee advanced.

Yes you get good colleges check official josaa site for opening and closing ranks for previous years.

Hope this helps you. All the best