IIT

You should do whatever you are passionate about, if you are interested in doing chemical engineering then go for it.

There are plenty of colleges in India, where you can pursue a degree in aeronautical engineering. The colleges are mentioned below:
PEC University of Technology.
Bengal Engineering and Science University.
Manipal Institute of Technology, Karnataka.
Amrita Institute of Technology and Sciences - Tamil Nadu.
Sathyabama University.

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

Hello Payal,
The number of seats in the IITs have increased as a result of the new IITs that were established recently. The total number seats in 2017 are around 11,000 which are filled on the basis of JEE Advanced.

All branches have equal scope in IITs and NITs but I would say ECE branch has wide scope in public, private and government sectors. Many of my friends from ECE got placed in ONGC, GAIL and even in IT sectors as analysts.

It may vary from 50000 to 1 lakhs but don't worry many coaching institute provides scholarship discounts of 10% to 75% depending on your percentage of class 10th and entrance exam conducted by the institute.