Dost thou think Alexander looked o' this fashion i' th' earth?
E'en so
The grave digger is telling the story about a crazy man known as Yorick, the king's jester. He was known for being crazy and evil.
Hamlet was remembering his old friend Yorik, and telling Horatio and the gravedigger how he was to him.
What ceremony else?
Hamlet ask Horatio about Alexander the Great, if he could look alike his old friend, receiving a positive answer from his friend.
Hamlet saw the King and Queen with Laertes and a priest walking to a grave. Hamlet told Horatio to stay and watch for a while.
Laertes was demanding a better ceremony for her sister, he was ordering the priest to bury her like the rest, the priest didn't want to for respect to the other non living.
Hamlet hearing the conversation understood that the person who took her own life was Ophelia, Laertes sister.