Hi Aspirant 

As you know the Syllabus is vast i.e entire 11th class and 12th class.Yes NCERT preparation for chemistry can be helpful but not for physics and maths.They are a bit vast that what you have read in NCERTs .So don't restrict yourself only to NCERT and don't assume by yourself this would be enough.There are lakhs of student appearing for the exam .So you can think of the level of paper.You should buy or arrange from your senior or friends the study material of either FIITJEE,Aakash or ALLEN .They can be helpful for your preparation.

All the best

Yes you are right NCERT previous years questions in concepts will help you not only to qualify JEE main but also to score very good marks in JEE main in fact many questions you will see in the exam or directly from NCERT specifically in chemistry most of the questions can be solved using the concepts of NCERT in physics and mathematics therefore justice league 2 NCERT as the last time preparation and solved previous years questions of JEE main and advanced both.