Dumb orator is already explained in the other SE.
"Post Office" does not refer to the 20th century kissing game. It was played by the following rules:
Each one of the participants writes a poem, anecdote, essay, or a letter to some person, either present or absent. Any one who chooses to do so, can disguise his handwriting. The papers are folded and addressed, and then deposited in a covered box placed on the table. A postmaster is chosen. The postmaster opens each letter, first announcing to whom it is directed, and then reads it aloud. The players try to guess who wrote each letter, the winner being the one who guesses the most correct. A side object is to write amusing letters.
"Hunt the Keyhole" is not a game. It is just a description of what you have to do when returning drunk to the house in the dark, or when returning to a door with which you are unfamiliar, like that of an inn. In the 19th century, porches were often unlit and doors had a wide variety of locking arrangements, so finding the keyhole could be difficult late at night.