Dear aspirant,

85%ile in JEE mains can be achieved by scoring approximately 60-70 marks, it can also vary according to the question paper.

Now, list of the chapter you should do for this:-

Physics :-

1.modern physics,

2.semiconductor

3. Ktg and thermodynamics

4. sound waves

Chemistry :-

1.surface chemistry

2.Coordination compounds

3.biomolecules

4.polymer

5.chemical kinetics

6.solid state

7.structure of atom.

Maths :- 1.statistics

2.mathematical reasoning

3.binomial theorem

4.quadratic equations

5. differentiation

6.sets and relations

7. LCD

So these are the chapter which are basics and have more weightage. Also i recommend you to cover all topics which will also help you getting more than 90%ile even.