Class 11

For physics : H. C. Verma or Arihant. For chemistry : NCERT is best. For Maths : TMH
But the main thing is to go through previous year JEE questions which will give you an idea and many of the questions will clear your misconceptions.

The candidate must have cleared 10+2 Science stream schooling with Physics and Mathematics as the main subjects (age of candidate should not be less than 17 years when the course starts).
* Non Science stream students may pursue the required subjects through NIOS. NIOS schooling can be used to meet the above mentioned requirements. Apart from NIOS, non Science stream students may also pursue the required subjects as private candidates from their respective state boards too!
* The minimum marks required is 50% (may vary from Institute to Institute) aggregate marks.

They check almost everything before they decide on the interviews.

That's a tricky part. I would suggest you get in touch with Delhi University officials for clarity on such things.

You can complete your class 12th with good marks, rest will follow automatically.

No,
You can apply for the NEET exam after class 12th .

Actually if you google it, The mentioned syllabus would only comprise of class 12th topics. Though the actual syllabi is as below:-For Maths the majority of the questions are from class 12th. Next Chemistry it consists questions from both classes. Mainly basics of class 11th. Lastly Physics it won't be wrong to say that weightage of both years in this subject is equal. This answer is totally based on my previous year experience. The syllabus was same as mentioned. Hope it's same even this year.

You can apply for the exam this year and you can check further details in official website of NDA.