Colleges in Rajasthan

Yes, NIOS students are eligible for MBBS.

No, it will not be possible as there is no engineering college/university in which session begins in the month of December or January, for details check the link below:
https://www.shiksha.com/b-tech/course/b-tech-in-agricultural-engineering-mahatma-jyoti-rao-phoole-university-jaipur-201809

It depends on the career prospects that one has attained. Still, going on the statistics, CSE students get higher salary package.

Hi Sajid, check out colleges and institutes and the eligibility here and apply:
https://www.shiksha.com/engineering/colleges/diploma-courses-india

You need to score at least 385 to get admission in BITS, Pilani for CS.
For JEE, textbooks are extremely important.
Physics- Cengage Publications (The best with strong concept development and solved examples explained very well) and H.C. Verma
Mathematics- Tata Mc Grew Hill
Chemistry- OP Tondon and RC Mukerjee
I am attaching a link of JEE Books that you will find beneficial if you want separate specialized books on each topic:
http://www.askiitians.com/important-books-iit-jee.aspx

The fee in BITS, Pilani for MBA course is around INR 7 - 7.5 lakhs for the two years course.