IIT

Super 30 is the best for the same.

Hard work, smart work, dedication, guidance, are the most important thing. First of all, finish your 12th syllabus first then revise concept of 11th as burden of board exam will not be there if you will follow this method. You can take help of private tuition or coaching centres. Take advise from your school teachers as they know you better and also from seniors who have cleared IIT exam.

It will depend on you if you confirm about that you can qualify JEE next year so you can wait for next year, otherwise don't waste your time anywhere to preparing for IIT.

No, it requires speed to answer and is at Mains level.

Admission in IIMs /FMS / IIT depends a lot on the score you achieve at CAT. The institutes mentioned by you are among the top ranked ones and to seek admission in any of them, you should air for scoring at least 98+ percentile score at CAT and also, do well at the Personal Interview for seeking admission.

Hello Krishna,
As per your rank, your chances nil for getting any nit's,however you may check here for more insights:
https://www.resonance.ac.in/reso/news/JEE-Main-Branch-Predictor.aspx

Hello Juned,
There is no drawbacks in dropping a year for good colleges, however you need to be very determined and need very good practice to score some good marks in JEE advance next year.
All the best.