The ones 'in prison' are the Fallen Ones... The Fallen Angels or Watchers who 'left their first estate' (gen 6), to lay with the daughters of men. And I don't think it was preaching - It was a declaration.
The good who died before the coming of Messiah were in a place of comfort called 'The Bosom of Abraham' which is now empty - These souls were presented to the Father by Yeshua upon the Resurrection as the 'First Fruits' offering that wonderful Sunday morning.
Correct.
Abraham’s Bosom, also known as “Paradise’ for Old Testament believers. Prior to the Perfect Sacrifice, no human could enter into the presence of God at His dwelling place in heaven, so they were provided Paradise, a compartment of Hades, the underworld, not to be confused with other portions of the underworld, the Torments, Tartarus, The Abyss and later the Lake of Fire.