1) It means where does the person get the money that they need to live. This could be a job, a pension, savings, spouse etc. These are their means of supporting their expenditure. Someone without any visible means must have invisible means, since they still must buy things, probably a criminal.
2) He decided to depart sooner.
4) Nope, it means the style in which he would tell the story. Bragging of cutting off 3 heads in a row, which probably didn't happen.
Henry, Prince of Wales. . . . I am not yet of Percy's mind, the Hotspur of the North, that kills me some six or seven dozen Scots at breakfast, washes his hands, and says to his wife, "Fie upon this quiet life! I want work," "O my sweet Harry," says she, "How many hast thou killed today?" "Give my roan horse a drench", says he, and answers "Some fourteen" an hour after—" a trifle, a trifle." I'll play Percy, and that damned brawn shall play Dame Mortimer, his wife. "Bibo" says the drunkard. Call in ribs, call in tallow.
(King Henry IV, Act II, Scene IV)
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