1. Sunken Gelnika Airship. You'll need to take the submarine and submerge when you get to the Gold Saucer. It's around there.

3. Morph a Ghost Ship found on the Underwater Path leading to the Junon Reactor. Take the Guide Book the to Kalm Traveller and he'll exchange it for the Underwater materia.

Best level would be 99, but you should be able to manage with Lv70ish.

4. As above. Enter the battle with two characters KO'd. W-Summon Hades and KotR. Link KotR to HP Absorb.

5. Earn 64,000 BP at the Battle Square.