how to prepare for jee advance being taken lower percentile in mains

The strategy is very simple. Now as there is not any much time left for the complete preparation. So the best thing to do is, revision through previous years question papers. Solve the previous 15 years question of jee advanced regularly till jee advanced exam honestly with accuracy and leave it one day before jee advanced exam. While solving previous year full length paper if you get stuck in any problem then after checking by yourself (honestly) revise the concept of that particular problem and also of that problem that you did mistake and again solve it. Regularly and daily give the previous years full test very honestly in real time for 6 hours, in other words, dedicate yourself to jee advanced and always think positive that you can crack this jee advanced exam. Never cheat while giving the practice tests by yourself. Also do some jee advanced level test series for better practice of some coaching institutes. Don't study the new things or topics that you did not know, because it will take time and affect you very gravely in your preparation.