IIT

NIT Surathkal, Gandhinagar, Kurukshetra are the best. You can also go for VJTI Mumbai, Sardar Patel Mumbai, BITS Pilani, ISM Dhanbad as they offer best placements into MNCs and conglomerates.

You can check the below mentioned link:
https://www.shiksha.com/b-tech/articles/best-books-for-jee-main-2020-preparation-blogId-19529

Hello Debargha Samanta,
Keep these points in mind before starting preparation for IIT:
Time management
Follow a schedule / prepare a plan.
Know the syllabus and the exam pattern well, weightage.
Coaching classes online or offline? Self-study.
Study concepts, solve problems and look at solutions.
Solve previous year's papers.
Take timed practice test series.
Group study, hangout more with toppers
Health is wealth.
Manage Distractions through self-control app.
Retrospect your day.

Hello Aman,
If you are clear about your career that you want to be in IIT then go for it. You can drop and start preparation but don't spoil one if it's not serious for you.

IITs and NITs do not offer degree course in BCA.

JEE exams are just tricky. Just clarify your concepts and then try. You will solve most of the previous year's questions and in JEE advance you need to use many concepts in same questions.
To get a good NIT you must secure 170+ marks out of 360 and total marks vary in JEE advance but to acquire a seat score should be 130+. If questions are very difficult then 100+ is sufficient to get a seat.

Hi,
Following are some best engineering colleges:
DTU, Delhi
NSIT, Delhi
IIIT, Delhi
GGSIPU, Delhi
LPU
Chandigarh University

No, for NIT you have to qualify JEE Mains and for IIT, JEE advance.