IIT

Refer to the CAT preparation books available like Arihant and Pearson Publications (for all the sections). Keep revising the important concepts and logics you come across. At this time taking test series is important, more you get the practice of CAT like exam more helpful it will be.

The curriculum is not entirely same but yes up to 90% it is same and for the detailed view/information you can visit the official website of the colleges to get the curriculum and compare, you will find that the 90% of the syllabus is same.

Hi,
Please find the links below to know detailed information on the same:
https://www.shiksha.com/b-tech/exams/jee-main
https://jeemain.nic.in/webinfo/Public/Home.aspx.

JEE Main is the first stage of the exam. So, it is not easy to crack it. You have to be highly dedicated and passionate towards study to qualify the JEE Main exam. Here are some tips which will helpful for you in your preparation. First of all, analyze the complete syllabus. Do not skip any topic. Prefer the NCERT Books. Because they cover all the topics of the syllabus. Firstly, complete your basics then focus on the most important chapters for JEE Main. Prioritize important chapters according to their weightage in the exam.

If you want to be an IITian, then you must have to start the preparation if JEE Main AND ADVANCE from now only with lots of hardwork, determination if you do not want to drop a year after 12th. Just go with the concepts of each topics carefully and practices every question of NCERT, then some good books of JEE Main. Practice previous year paper of JEE Main and advance also. Also try to get mock test of the exams and test series of some reputed coaching institute. Do self-study more and more.

If you do not want to leave your state, then don't aim for IITs and NITs.

No, you should study B.Sc Physics only in order to get admission for M.Sc Physics.

If you have confidence that you can get CS branch in any of the central government colleges then only I'll suggest you take a drop of 1-year, otherwise, not as you can also see what is the condition of the engineers in day to day life.

If you just now cleared your higher secondary education level, you must prepare yourself for JEE Mains and Advanced exams, by well preparing and lot of mathematical skills you pursue your IIT seat.
If you finished your Bachelor's degree, you must prefer GATE exams.

https://www.goabroad.com/articles/intern-abroad/inexpensive-internships-abroad
Go through the link.