Answer to Question 1
The rings of Neptune are bright in forward-scattered light and that indicates the rings contain significant amounts of dust. The narrowness of the rings suggests that shepherd moons must confine them, and a few such moons have been found among the rings.
Answer to Question 2
The rings of Uranus were discovered in 1977, when Uranus crossed in front of a star. During this occultation, astronomers saw the star dim a number of times before and again after the planet crossed over the star. The dips in brightness were caused by rings circling Uranus.