Design Entrance Exam

You can check the link mentioned below:
http://www.nift.ac.in/admissions.html

Yes, you can. You may check the eligibility criteria on www.nift.ac.in

Refer to the links below:
NIFT - http://niftguru.com/nift-faqs/
NID- http://admissions.nid.edu/faq.aspx

You will have to appear for entrance test which is conducted by NIFT, to get admission in the same.

Refer to the link below:
http://www.nift.ac.in/regularmaster.html

No, maths in not a compulsion if you wish to enter into the fashion designing field.

Refer to the link below:
http://stuffyoulook.blogspot.in/2015/05/books-and-study-materials-for-uceed.html

If you have done textile engineering then PG from NIFT will be a better optiin because NIFT is related to designing. M.tech through GATE also have options for pursuing course related to designing but. there are very few colleges and courses available in this case. Hence go for NIFT.