Looking for some help.

Father entered the country as a green card holder, GC confiscated at port of entry but was allowed in under deffer ed inspection. Went to the appointment, and after one hour of interrogation, he took the option to file an I-193 and GC was returned to him. So the questions are:

1. How would that affect his naturalization application when he files one in the future.

2. If he leaves the country, would he have problems returning after few months?

3. Is there a form he should fill out prior to leaving so he won't have these problems again.

thanks for the help.