IIT

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.

IITs are autonomous central government institutes of international repute with best faculties, facilities and infrastructure for engineering education. NITs are state regional engineering colleges with good facility for technical college. In India IITs are best institutes for engineering degree and NITs follow it closely in ranking. As IITs attract best talent through JEE, students of IITs are most preferred students by large corporations and MNC in campus recruitment.

You may refer to the following link for a list of top aeronautical engineering colleges in India : https://www.shiksha.com/top-aeronautical-engineering-colleges-in-india-rankingpage-49-2-0-0-0

For ethical hacker, you need to take some other specialisation course. It will be a certification course. IIT JEE is required to pursue engineering in different fields.

Hi,
Yes, there is a reservation for physically handicapped student in IIT.
Persons with disability (PWD) 3% seats in each of open, OBC-NCL, SC and ST category seats. The benefit would be given to those, who have at least 40% impairment irrespective of the type of disability i.e., locomotor, visual or severe dyslexic.
Leprosy-cured candidates who are otherwise fit to pursue the courses are also included in this sub-category.
You can check the below mentioned link for further details:
http://www.jeeadv.ac.in/info_brochure
All the best.

Yes, it is necessary to clear IIT-advanced to get admission in IITs.