IIT

yes, but if you have studied in coaching institutes for two years or you have solved jee books still can't clear jee mains then do not drop a year, many options are there, try wbjee, jcece etc.
BUT if not solved any jee books or not prepared for jee yet, you should first prepare for it then only you will know your capacity. it will also help for future plans which branch to choose. you will go to a college where other students have read jee books so you will have tough competition.

Awesome scope if its from IIT

you should understand that life is possible beyond IIT too so don't worry just give your 100% and ifnot IIT many other good institutes like NIT , BITS pilani , VIT, are there so don't worry give your best.

You cannot go for IES with CSE but yes you can opt for any of the civil services after graduation. Also if you still want to appear for IES after CSE, you will have to choose electronics for your mains exam.

This is happening because you have taken a lot of stress and maybe you are doing the same chapter for a long repeated time .Avoid this tendency and don't stick to a single chapter and please don't take stress otherwise it may harm your JEE results .just keep calm and devote your best you will definitely succed .
Best of luck for your JEE advanced.

MY FRIEND JUST ERASE ALL THOSE BIG INSTITUTES NAMES FROM YOUR MIND AND GO FOR SOME OTHER COURSES LIKE BCA,MERCHANT NAVY
OR GO FOR SOME LOCAL UNIVERSITY IF U REALLY WANT TO DO BTech

Hello Neha. Every year there is a cutoff in JEE Mains that needs to be crossed to appear in JEE Advanced which is a test for admission in IITs. This year this cutoff is expected to be around 100-115 marks in JEE Mains.