IIT

If you are talking about last year's opening and closing ranks, then these are already declared on the josaa. Nic. In
And, for this year's ranks, firstly the result of JEE Advanced will be declared and then the time table of whole counselling procedure will be made available on the JOSAA website. Generally, the counselling starts in last or second last week of June.

Yes you are. You might even get your preferred course.

No, there would not be any problem in dropping an year for JEE. And I am not sure about which interview you are talking about but No one will ask about reason for your drop and even then somebody asks you then the answer is obvious "I want to improve my JEE score"
You just have to give an affidavit for your drop which is easily made. I also have dropped an year and there is no need to give someone any reason for that.
Best of luck.

No, there is no such exam. Moreover, IIT-JEE is only held only for central government run institutions across the nation.

I would rather suggest you to go for IIT first and do not lose your 1 year in B.Tech. If you don't have the option right now then you should study and prepare for the entrance exam of IIT then if pass then further procedure will start.

I think you should study class 11th, class12th and prepare for IIT-JEE.

It's all on your interests. According to your marks, you can easily pursue B.Tech in IPU. But, if you have full faith that you can crack the next year IIT entrance exams, then only go for one year drop. Otherwise, if you have doubt then do not take a risk of one year. My suggestion is don't go for one year drop, pursue B.Tech in USIT, and then score good in college. All the very best.

For IITs, you must be really consistent with your studies. You may join a coaching institute (VMC of FIT-JEE) and prepare simultaneously with your board exams. But if you wish to prepare on your own, gather GOOD study material (buy coaching institute modules), but do not collect too much material, only get what is required. First get your concepts crystal clear and then move on to numericals. Solve as much questions as you can. Practice daily. Give more time to mathematics and then physics. Word hard and forget everything. Good luck!

Choose Science stream in class 11th with mathematics as a compulsory subject. You may opt for computer Science as an additional subject. Good luck!