I am planning to go Nepal in TPS advance parole(AP) to visit my family. if someone has parole document and already been to Nepal in AP, you must have a idea on the followings: please share

1. I am having difficulty what reason should I show to get the AP. What evidence do I have to show to get TPS Advance parole. Do I just need a letter explaining the purpose of my visit, Should the purpose of visit be only family/relative medical condition ? my family is well back there.
3. How long does it take to get Advance parole approved.

4. Generally , for how long the AP is granted.

Thanks