The Grand Duchy of Lithuania / DUCHY The Principality of Monaco / PRINCIPALITY - What is the difference between the two words? - Which word reflects the higher status of a state?

After a long talk with the harbor-master, Captain Leclere left Naples greatly disturbed in mind. In twenty-four hours he was attacked by a fever, and died three days afterwards. "Why, you see, Edmond," replied the owner, who appeared more comforted at every moment, "we are all mortal, and the old must make way for the young... «The Count of Monte Cristo» by Alexandre Dumas

Hello! "Harry must HAVE HAD more haircuts than the rest of the boys in his class put together, but it made no difference, his hair simply grew that way - all over the place." Could You tell me please which grammar rule this example belongs to?

Hello! Could You please remind what is the tense: "Harry WAS USED to spiders / When he WAS DRESSED he went down the hall"

Hello! Could You please tell me: He chuckled and muttered, “I SHOULD HAVE KNOWN.” - What is the tense?

Hello. Could You tell me what is the time, please? "Mrs. Dursley HAD HAD a nice, normal day."

Hello guys! Could You check this sentence: "This shirt gifted by her." Have a good time!