Anyone who is an Indian citizen by birth but for employment or other vocational reasons, stays outside India for an indefinite period time can be all as a NRI.
Person-of-Indian Origin can be people who are citizens of a foreign country, but who was born in India or whose father and forefathers were of Indian origin.
These are bodies largely owned by people who are Indian citizen or of Indian origin but reside outside India. They include overseas companies, corporate bodies and partnership firms owned mostly by the Indian citizens or people of Indian origin. In these bodies, three-fourth of the interest is owned by Indian citizens or people of Indian origin.
Yes, it is absolutely possible for them however, through the RBI and Government way which includes, Foreign Investment Promotion Board (FIPB). These Individuals and bodies can invest up-to 100% equity in Indian real estate and civil aviation sectors. Their investment in India is fully repatriable except in case of real estate which has 3 years lock-in period on original investment along with 16% cap on dividend repatriation.
Payments can be made either out of inward remittances in foreign exchange through normal banking channels or out of funds from NRE/FCNR accounts in Indian banks.
Any number of commercial properties can be acquired by them, as long as they can afford it legally.
Yes, they can do so.
Yes, they can do so through approved banking channels however, after submitting their remittance forms to Reserve Bank of India. Maximum limit of sending remittances are US$ 100,000 a year.