Non resident taxability

Background regarding my query.

1) Assessee is a senior citizen, residing in USA for the past 2.5yrs.
2) He isn't employed in USA.
3) Assessee has not filled return claiming NRI status till date in India, so for income tax purpose he is still a R&OR.
4) Has investments in Term deposit/FD with nationalized bank/private banks and MF as a R&OR of India. He has submitted Form 15G seeking non deduction of TDS on interest income.

following are my query's.

1)Whether the assessee has to compulsorily declare himself as a NRI in his ROI, if yes, what are the consequences if he doesn't do so?

2)whether the present investment in saving/term deposit can be assessed as a resident assessee or is it to be converted into NRO/NRE account.

3) what is the rate of TDS for NRO account for person staying in USA under DTAA.