Did everyone in the Middle Ages have to be Catholic?

Answer 1

Not really, but pretty much they were. There were times when the Jewish population of an area were told to leave or killed ( many of Columbus crew were Jewish because they had to meet a deadline in Spain for leaving). In Venice a bell tower was built at St. Marks square that rang at sundown telling the Jewish population that they needed to be behind the gates of the ghetto where they lived. So, the Muslim and Jewish populations were there, but not treated very well.

2nd Answer: Protestant Christianity did not arise until after the end of the medieval period. The churches of western and northern Europe were Roman Catholic. Churches of some parts of Eastern and Southern Europe were Orthodox. The two churches formally divided in 1054 over a variety of issues.

There were Jewish populations in Europe at various times and places in the middle ages. Also, Muslims had conquered the Iberian peninsula in the 8th century, and were not fully driven out by Christians until 1492. During the early middle ages there were still pagan populations in Europe, but these converted or were conquored over time. Most areas of Europe were Christian by the 12th century, although a few areas held out somewhat longer.