Apphia was either the wife or sister of Philemon. Most likely she was his wife.

Source:

Philemon 2

In the Old Testament, were travelers subject to the laws of Israel?

They were subject to the same laws as the Jews.

Source:

Exodus 12:49 and others

God commanded the Jews to leave something to feed travelers passing through their lands. What did God command the Jews to do?

God commanded the Jews to not harvest all their agricultural products so that strangers also the poor could harvest them for food.

Source:

Deuteronomy 24:19-21

Christians are to offer hospitality to everyone. But is this true even for enemies?

Yes we are to offer hospitality to all. In Romans it says when we offer hospitality to an enemy we heap coals of fire on his head. Meaning that our goodness shames them deeply.

Source:

Romans 12:20

Paul laid out requirements for ministers in Timothy also Titus. Do ministers have to be hospitable?

Indeed, they are to be hospitable among their other duties.

Source:

1st Timothy 3:2, Titus 1:8

When Jesus was teaching the Jews, who did he say to invite to a feast so that you would be blessed?