Short answers, pulled from the story.
A complete performance of Der Ring des Nibelungen takes about fifteen hours of playing time, spread across four nights at the opera. Das Rheingold, the shortest and first part, runs roughly two and a half hours with no intermission, while Götterdämmerung, the longest, can last up to five hours excluding intervals.
The first complete Ring cycle opened the first Bayreuth Festival, running from the 13th to the 17th of August 1876. Das Rheingold opened on the 13th of August and Götterdämmerung closed the cycle on the 17th.
Wagner drew on Old Norse Edda texts for Das Rheingold, the Völsunga saga for Die Walküre, and a combination of the Eddur, Völsunga saga, and Thidrekssaga for Siegfried. The Nibelungenlied, a twelfth-century German poem rediscovered in 1755, appears to have been the original inspiration and is the primary source for Götterdämmerung.
A leitmotif in Der Ring des Nibelungen is a recurring musical theme or harmonic progression that musically represents a character, object, emotion, or action in the drama. Wagner described them in "Opera and Drama" as "guides-to-feeling," comparing their function to the Greek chorus in ancient theatre.
Wagner commissioned the Wagner tuba, invented to fill the tonal gap between the horn and the trombone. He also revived the contrabass trombone with a double slide, introduced a bass trumpet, and developed the Wagner bell to allow the bassoon to reach a low A-natural.
The first UK staging of Der Ring des Nibelungen was organized by London impresario Alfred Schulz-Curtius, conducted by Anton Seidl and directed by Angelo Neumann. It took place in 1882.