Why is Tolkien’s world called Middle Earth? If it’s called Middle earth, then is there an Upper earth or Lower earth?

Since Aragorn is a king, and a descendant of Isildur, is Isildur then of royal descent as well?

Why are the king dwarves all named Durin and how many are there??

Describe the rings of power?

Which Durin gets killed by the Balrog?

Who do you think are those characters who went to visit the crater made by the “meteor man”?