Exam

Yes, a commerce student can take admissions at NIFT as well. For Bachelors programs, you should have an education of 10+2 equivalent, And for Masters Programs, you should have a Under-Graduate (UG) degree. Now just to give you an idea about the NIFT entrance examinations (overall):
There are five components in the exams: GAT (General Ability Test), CAT (Creative Ability Test), Situation Test, Group-Discussions & Personal Interview
The structure and weightage of the questions varies for Bachelors & Masters programmes.

Yes, migration is possible within the university and within the state , you can contact the university for the same. There is an official procedure for it which you have to follow.
hope for the best
good luck

JEE Main Score Card Validity
JEE Main score card is usually valid for one years after JEE Main results are declared. Candidate can make use of the score card up to one years for attaining admission in their choice of institution. You can contact to NATA for official information.

Yes, it offers Lateral Entry admissions to Diploma Engineering students. But limited branches are there. It is very difficult to get the same branch as you have in your Diploma Engineering. Here I am providing a link for your help
https://www.shiksha.com/university/Delhi-technological-university/dtu-leet-exam
Kindly follow the link to know all the important details.

You can attempt JEE Mains for 3 consecutive years. You have already given JEE Mains first time in 2019, so now you have to 2 chance in 2020 and 2021.

Hello Rajeevan,
Please predict your college through this college predictor. The rank predicted might be accurate, but it certainly gives an idea to the aspirant.
https://www.shiksha.com/college-predictor