OCI, PIO and FN candidates will not be eligible for admission in NITs or IIITs through JEE Main. In NITs, IIITs, admission will be done for such candidates through DASA.
However, such candidates need to appear in JEE Main and then Advanced for IITs admissions. Eligibility criteria regarding educational qualification, age limit, attempts, are same for Indian candidates as well as others.
Are Person of Indian Origin (PIO) treated as foreign nationals? Can PIOs appear for IIT JEE Advance Examination.
According to the brochure, candidates will be treated in two categories only - Indian and Foreign Nationals. However, I would strongly advise you to contact individual IITs as such norms vary from college to college. You can contact the top IITs such as Bombay, Delhi, Kanpur, Kharagpur and enquire about their specific norms. As far as my understanding goes, I think you will be treated as FN only.
How many supernumerary seats were allocated in previous years (2014, 2013, 2012, 2011 & 2010) and what were the open rank and close rank for these supernumerary seats.
As per JEE 2014 report (link - http://www.iitk.ac.in/new/data/jee-report/JEE-2014-Report.pdf )
- Two (2) supernumerary seats were created to foreign nationality.
As per JEE 2013 report (link - http://www.iitk.ac.in/new/data/jee-report/JEE-2013%20Report.pdf )
- One (1) seat was allotted to FN candidate in IIT Kanpur. Whether other IITs allotted any such seats is not clear.
As per JEE 2012 report (link - http://www.iitk.ac.in/new/data/jee-report/JEE-2012%20Report.pdf )
- Ten (10) supernumerary seats were created due mainly to issues related to the category certificates. In
addition, ten foreign national candidates were allotted supernumerary seats.
As per JEE 2011 report (link - http://www.iitk.ac.in/new/data/jee-report/Report%20JEE%202011_EDITED_Aug14.pdf )
- Seven (7) supernumerary seats were created for the Foreign Nationals.