Income tax return for nri

Is your friend's status is Resident or NRI ?

If NRI then no tax on salary income in UAE.

Transfer of funds to his father's account in India will be in the form of a gift and it will not attract any income tax.

Income Tax Return of your friend can be filed as NRI (if he is) in so far as his Indian income is concerned.

it will be a belated return under 139(4) and can be filed upto 31-3-2020 subject to a late fee payment as applicable.

He goes to UAE country before 2 years