Was tennis strictly a sport for the aristocracy, or did it cross social classes?
Tennis, as played then, is what is called "Real Tennis" today (as opposed to "Lawn Tennis").
Real Tennis evolved in the court of France. It spread as an aristocratic pursuit across Europe. It was played in a rather large building or courtyard, and the walls and roofs surrounding the court were part of the field of play.
There are only 47 Real Tennis courts remaining in the world today. The oldest of which is at Falkland Palace in Scotland. It was built in 1539. The Real Tennis court at Hampton Court Palace in England was built in the 1620s, but built on the site of an earlier Real Tennis court from 1528.
Real tennis was strictly a sport for the aristocracy. It did not cross social classes.
I don't know much, but according to my history teacher, it wasn't really a tennis court - more like handball, or a variant of it.