the order is paradox irony satire pun
he discovered that the sword Hrunting is useless against Grendel's Mothere's hard skin.
I believe it is the compass. It aided sailors locate the direction to which they needed to go. Even before the age of exploration, people had ships capable of long voyages. As the years pass, the designed improved to an extent that they can travel farther.
Yes as long as you can tell your friend when you told them the idea .