IIT

Except IIIT Hyderabad for CSE, BITS Pilani in some of its courses. No other college is comparable to an IIT. Though, there are many good colleges but you can keep them in competition with good NITs but never against IITs.

There are two ways.
First, apply through the various internship programmes. Keep a check on Internships in India | Internshala for updates on such programmes to various IITs.
Secondly, the one I prefer, start preparing a mailing list of email ids of professors, visiting the websites of the IITs you'd prefer to intern at, and start mailing them, modifying your cover letter a bit for each prof. Send around 100-200 mails to different profs.
P.S. I got an internship in the latter process.

Dear,
To get Admission in any IIT, you should have a minimum of 75% in class 12th with PCM.

Hello,
For becoming an IIT engineer after class 10th you have to take science and maths stream. And for cracking IIT exam, join a recognized coaching institute in your area which is providing IIT coaching.

It is around 12 lakh rupees per annum.

Hello Neha,
IIT's are the best in India.

Hello Jyoti,
For joining IIT for civil engineering you have to appear in JEE Mains and Advance and if you want to join PG Program then you have to appear in exam GATE. I hope you understand that both the exams are compulsory to appear for joining IIT but both are at different level.

30000 students were selected, not 50000. There are other institutes than IITs like RGIPT, IIPE, IIST and ISCER giving admission on the basis of JEE Advanced. In fact, IIPE took rank around 30000 in its 2nd round and RGIPT took around 20000 in 2017.

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