The Normans
In Chaucer's time, Middle English was the language spoken in England. It was a transitioning period between Old English and Modern English, and during this time, English was heavily influenced by French due to the Norman Conquest.
French
The Canterbury Tales were written late in the 14th century in England, and the Tales are contemporary to that time. All indications are that Chaucer was using the English of his day.
English was spoken in England during Tudor times, specifically Middle English in the early Tudor period (late 15th to early 16th century) and Early Modern English in the later Tudor period (late 16th century). The Tudor monarchs themselves primarily spoke English.
No, the old English language did not stop in 1066. The Norman Conquest in 1066 influenced the development of Middle English, which gradually replaced Old English as the dominant language in England. Old English continued to be used in some contexts alongside Middle English for a period of time.
During the medieval period, middle English changed to modern English.
The Norman Conquest of England in 1066 marked the beginning of the modern period of the English language. This event introduced significant French influence into the language and led to the merging of Old English and Norman French, resulting in Middle English.
William 1 conquered England in 1066
Middle English typically describes dialects of the English language dating back to the Middle Ages. The time period for this dialect was between the High and Late Middle Ages, thus giving it the name "Middle English".
It's not an Old English word--it didn't enter English until the 1300s which was definitely in the Middle English period. Nor is it totally obsolete, although it is now confined to dialects in Northern England and in Scotland. It means "sneeze".
The Commonwealth, or Commonwealth of England, was the period from 1649.
During the Early Middle Ages, there were a large number of English kingdoms, most notably Wessex, Essex, Sussex, Kent, Mercia, Northumbria, and East Anglia, though there were several others. These kingdoms fought with each other, the Welsh, the Scots, and the Danes (Vikings). After England was conquered by the Normans, the English fought mostly with the Welsh, the Scots, and the French, but they also fought in the crusades and in a number of places in Europe.