1)
What is the significance of the three times that the word "Kos" is mentioned in the chief butler's dream?
1.
Chulin 92a: They represent the three cups of punishment that Pharaoh (Egypt) is going to drink - one in the days of Moshe, one in the days of Pharaoh Necho, 1 and one together with all the Nochrim.
2.
Rashi (to Pesachim 108a): The three in the current Pasuk correspond to the three [extra] cups in the Pesach Seder - of Kidush, the Hagadah, and Hallel. (The fourth cup is the usual cup for Birkas ha'Mazon. 2 )