JEE

It depends on the category, which you belongs to. If you are from SC category, then you will surely get it, but if you from general category, then you won't be able to get it.

Material, biochemistry, energy, biomedical
Bits, DU , GU

No need to wait. Just go for it.

For that, I'll prefer you start doing self study as more as you can as this is the only that will help you the most and for that if you want any help regarding any topic then you can directly go to the top websites such as coursera, edx and many more, from there you can clear your doubts.

The best and most successfully accepted, widely used tip is, Do smart work rather than hard work.

Yes, joint entrance exam is one of the mandatory exam required for admission in NITS, IITS, IIITs and many other premier institute of the India.

It will be declared in the last week of August.

Basically, it depends on the college in which you are taking admission, as in some private college they take their own entrance exams and acknowledge the same for the admission and in some colleges they also take admission through JEE Mains score.

See, changing current college doesn't guarantee that the next college in which you take admission is good and up to the mark of expectation and in almost all the government colleges teaching is not quite good. So, I'll prefer you to take up the responsibility on your shoulder and start learning on y

You can visit Kakadeo for the best coaching centre. Some options are:
KalraShukla, Akash and Ashish Vishnoi.