Hello Sayam

It is difficult to predict the actual rank or JEE Advanced qualifying marks as for the first time JEE Main is being conducted twice and rank will be based on NTA percentile score but you may calculate your expected rank by this formula-



874469 are the number of candidates appeared for the January exam. So rank formula is (100- your total score) * 874469 / 100.
If the number of candidates for April exam increased to 1400000 then your final rank shall be (100- your total score) * 1400000/100



It's difficult to tell you the exact qualifying marks for JEE Advanced Eligibility but if you are getting more than 85 percentile score then you have decent chances to qualify for JEE Advanced.



Good Luck!