JEE Main

You need to score around 150 marks for outside Punjab. To get admission in Punjab, you need to get 110-120 marks.

For practice purpose, you may go for other books too, as they've vast number of questions and exercises. You can also check the previous question papers.
All the best.

VIT is in top 20 engineering colleges of India. If you are able to get VIT after dropping a year then its worth a try option.

You should read your 11th and 12th NCERT textbooks perfectly and then go for HC Sharma for physics.

Hello Pranjal,
Don't drop a year. First, appear for other state level entrance examinations like OJEE, EAMCET, COMEDK, etc. You may get a good option in those exams. If you still don't get good score then you can drop a year and prepare. You can join a good engineering coaching institute as well. Remember, if you drop a year, the competition will increase. Many more would have dropped a year like you and the fresh upcoming batch too will be competing. Think judiciously.

Yes, you have a chance if your rank is good but not a desired branch.

If you cleared IIT-Mains, then you are eligible to get admission in any decent engineering college. A score around 190-220 is a good score to get into NITs. You can try to score good in IIT-JEE Mains, so that you can fight for IITs.

You should concentrate more on chemistry and physics. You need to focus on the last 5 chapters of class 11th and 12th.
All the best.

No, it is not mandatory. You can write college specific entrance exams.

If you get 200 marks in JEE, you can get any NIT. So, first prepare well and get good marks.