HELLO SIR
since it is very difficult to predict the exact rank but we do have a backup we have a formula to calculate the expected rank that is (100 – Total percentile) x 869010/100.So according to formula your expected rank for present percentile for January session comes out to be 8777. Now the expected rank might change depending on the no of candidates appearing the april session. For ex if 12 lakh candidate appear the april session then just replace 869010 by 12 lakhs. But if you score above 85 percentile then you have a very decent chance of qualifying jee mains.
WEll with the present percentile he may get some good colleges.
But get TOP 5 NIst in CSE branch might seem alittle difficult for general categorey.
No worries since you have an april attempt left and most importantly baap of the exams i,e Advance which may directly lead you into IIts.In the april session just try to score a percentile above 99.6+ so that top 5 NITS are in your hand.
There are tons of engineering entrance exam which are equally important to JEE mains.
there are some reputed institute which offer their own entrance exam such as ,SRM,BITSAT,VITEEE etc.
i'll provide you a link where you will get all the engineering entrance exam of india https://engineering.careers360.com/exams

But if you are curious to know that which college you might land into with your percentile then you can use the college predictor link which has following features;

JEE Main 2020 College Predictor

Know your college admission chances based on your JEE Main Percentile, Home State, Caste, Gender, etc

Including premium institutes like NITs, IIITs and CFTIs, many States/ Institutes accept admissions through JEE Main. Know your chances in states like Maharashtra, West Bengal, Delhi

Get your personalised JEE Main report with Top Predicted Colleges in JoSAA & State Level Counsellings delivered on mail

2.5 Lac engineering aspirants used Careers360 College Predictors

*B.Tech Companion*

Your one-stop B.Tech Counselling package with Full-Length JEE Main Mock Tests, 15+ College Predictors, a printed Almanac with 1000+ FAQs on Admissions & more

https://www.careers360.com/btech-companion

ALL THE BEST FOR APRIL AND ADVANCE!!