I have travelled several times on AP (including land border) so I am just sharing my experiences and views. I am not a legal adviser though so do not take in that way. As far as your AP and passport is valid, you may good to travel and return back. Nepalese immigration officers and airline staffs at TIA are aware with AP or form I-512L. You will have your documents checked before boarding into the plane each time (even during transit). Once you enter into the US airport or pre-clearance facility (only few in the world including in Abu Dhabi, Toronto and Dublin), an officer will take your photo, fingerprint and escort you into the secondary waiting area for the parole stamp (because primary officers only have admitted stamp). Then chill, relax and sit patiently! You have to wait couple of minutes until they call you and return back your documents with PAROLED stamp. Then welcome to the US!