Need to consult green card information

[Neil_2004]

Guys

I just need to inquire very importatnt information my nephew is currently age 20 and he is in second year college and getting greencard by end of this year. If he want to go back to India to complete his study Is it possible to get reentry visa? or Is that any other way to hold visa process untill his graduation complete. Your guidance would be appreciated

Thanks in advance

[Xkuger]

He can apply for a extend stay outside i.e. 2 years once.

He has to main tain residency for at least 6 months a year in the US.