About 130-124 BC in the land of Zarahemla.
Benjamin taught his sons so they could understand the prophecies of God.
If it weren't for the records (brass plates / scriptures) even Lehi's family would have become lost.
Benjamin hands over the administration of the kingdom to Mosiah, which would possibly result in there being two kings reigning at the same time. This was not uncommon in Israel where a new king would be phased in.