Short answers, pulled from the story.
The original Broadway production ran from its opening on the 26th of January 1988 through its final performance on the 16th of April 2023, totaling 13,981 performances. That makes it the longest-running show in Broadway history, surpassing its nearest rival by over 3,500 performances.
Michael Crawford played the Phantom, Sarah Brightman played Christine Daae, and Steve Barton played Raoul in both the original 1986 West End and 1988 Broadway productions. Crawford won both the Olivier and Tony Awards for Best Actor in a Musical for the role.
Designer Maria Bjornson created the half-mask after the original full-face mask worn at the 1985 Sydmonton preview proved unworkable. It obscured the actor's vision and muffled his voice, so Bjornson designed the now-famous half-mask as a replacement, and the unmasking scene was added as a consequence.
Yes, on multiple occasions. In 1987 the heirs of Giacomo Puccini sued over a passage in 'Music of the Night,' claiming it resembled a phrase from La fanciulla del West; that case settled out of court. In 1990 a Baltimore songwriter named Ray Repp sued over the title song; after eight years the jury found in Lloyd Webber's favour. Roger Waters of Pink Floyd also publicly noted the similarity between the title song's main riff and 'Echoes' from the 1971 album Meddle, but did not take legal action.
Total estimated worldwide gross receipts exceeded $6 billion, with Broadway alone generating over $1 billion. The show held the record as the most financially successful entertainment event until The Lion King surpassed it in 2014.
Yes. Love Never Dies, written by Lloyd Webber along with Ben Elton, Frederick Forsyth, and Glenn Slater, is loosely adapted from Frederick Forsyth's 1999 novel The Phantom of Manhattan. It opened at the Adelphi Theatre in London's West End on the 9th of March 2010, received mixed reviews, and a planned Broadway opening was eventually cancelled.