I am a U.S. citizen and my father came here to the U.S. on a 6 month visitor visa. While here in the U.S., I have petitioned and already sent the required forms- (I-130, I-485, I-765)- to adjust his status to permanent resident. USCIS has already received and sent me confirmation numbers. My question is: Is he required to leave and exit the U.S or can he stay here while awaiting decision on his case to be granted adjustment to permanent residency? Thank you.Also, is it necessary and required of him to apply for visa extension form I-539? And can he stay here without having to request and apply for an extension? Thank you!