Please read all of Act I, sc. 2. Hal's & Falstaff's dialogue -- largely in prose -- should feel similar to the words of Sir Toby and Sir Andrew: it's back to the language of taverns, brawls, insults, & carousing.
Here's my rough time-line. Henry IV (Bolingbroke) usurped the English throne in, or anyway near, the year 1400 (...and yes, I did misspell the word 'Bolingbroke' in my crude chart below -- sorry!):
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