Around 1:39:00 Johan Struensee gives Laudanum (tincture of opium) to the Queen to sedate her. He pours it in a handkerchief and she inhales it. Opium however is a solid and does not evaporate; it must be drank.
While all of the characters all speak Danish in the film, the court language in Denmark at the time was German. In real life neither Graf Bernstorff nor Johann Struensee spoke any Danish, and it is probable that Christian and Caroline also conversed in German rather than the "people's language." However, this is a movie made for a Danish audience. "Translating" the characters' speech to the language of the audience is in the same principle as Hollywood movies where Egyptian Pharaohs and Roman Emperors speak English.
The Danish colloquialism "rolig nu" ("easy now"), which dates back only to the 1990s or so, is used by characters in the 18th century. However, as they really would have been speaking German, it is acceptable to "modernize" the translation.
During his first meeting with the doctor, the king says he likes "hookers with big breasts". While hooker is a 19th-century American word, it appears here as an English subtitle to translate Danish dialogue from a character who historically spoke German. In movies, some modernizing of what the characters "really" said in another language, is allowable.
In 1769, when Queen Caroline Mathilde is taking tea with the Dowager Queen Juliane Marie, they are clearly seen to be drinking from Danish Flora Danica cups. The Royal Danish Porcelain Factory was not established until 1775 and the service was not put to use by the Danish Royal Family until 1803.
The film's opening captions include the phrase "Europe at the close of the 18th century" and also "England, 1766." These two statements are mutually exclusive. 1766 was not the "close" of the century, it was just barely short of two-thirds of the way through it.
Queen-Dowager Juliane-Marie tells the servants that not reporting the affair is a mortal sin which will condemn them to purgatory. Juliane's religion was Lutheranism, which does not acknowledge purgatory or the concept of a "mortal sin".
Queen Caroline mispronounces the city of Celle as "Sell-uh"; it should be "Tsell-uh".