Dear Kaushik, if you are in Class 11, you will not have knowledge of 12th topics yet. So it is always important to focus on 11th topics in Physics, Chemistry and Mathematics. Use this year to strengthen your basics, fasten your calculations and practise problem solving. Make a timetable and stick to it. Try to attempt atleast 1 mock test per week. You might not be able to score on 12th topics but try to work on all 11th topics. Memorise formulae and make sure you take short gaps between your study schedule. Follow NCERT because most of the times, NTA doesn't go beyond NCERT.