1.About how long in earth time did it take for the children to come after they heard Tirian’s call for help? How long was it in Narnian before they arrived?

Nearly a week ago

Tirian said his dream let him into his world scarce ten minutes since

2.About how long had Rilian been dead since the children were last in Narnia? How did the children think they would get into Narnia? Why didn’t that work?

Rilian has been dead over two hundred years.

The Professor said the only way would be by the magic rings but actually they just arrived Narnia suddenly.

Because Aslan did it all for children in his own way without any rings.