Short answers, pulled from the story.
The Tragedy of Hamlet, Prince of Denmark is the longest play ever written by William Shakespeare and requires more than four hours to stage. This duration exceeds the typical two to three hour Elizabethan performance standard.
The ghost that haunts the Danish court is the recently deceased King Hamlet who appears to his son Prince Hamlet. The apparition reveals that he was murdered by his brother Claudius who poured poison into his sleeping ear.
The First Quarto of Hamlet was published in 1603 and is often referred to as the bad quarto. This version contains only about half the text of the later editions and is believed to be a memorial reconstruction by actors.
Sigmund Freud proposed that Hamlet's hesitation to kill Claudius was rooted in an unconscious Oedipus complex. The theory suggests the prince was unable to act against the man who had done what he himself had unconsciously wished to do.
Richard Burbage likely played the title role of Hamlet in the early days of Elizabethan theatre. He was the leading actor of the Lord Chamberlain's Men and performed the role during the play's initial run.