Short answers, pulled from the story.
The Beatles in Mono is a boxed set compilation of the remastered monaural recordings by the Beatles. It was released on compact disc on the 9th of September 2009 and on 180-gram heavyweight vinyl on the 9th of September 2014, with the vinyl versions cut directly from original analog tape sources.
The Beatles worked closely with their engineers on the mono mixes throughout the recording process, while stereo mixes were often completed afterward without the band present. George Harrison explained that mono felt natural because early studios used a single central speaker, and he felt stereo made the sound naked. John Lennon called the stereo mix of his song Revolution "a piece of ice-cream" compared to the mono version.
Yellow Submarine, Abbey Road, and Let It Be are not included because no true separate mono mixes of those albums were ever issued. Any mono versions that existed were fold-downs from the stereo mix, not independent mono productions.
The remastering project was led by EMI senior studio engineers Allan Rouse and Guy Massey. They oversaw the remastering of both the mono and stereo versions released on the 9th of September 2009.
Billboard reported 12,000 copies sold in the United States in the first week, where the set debuted at number 40 on the Top 200 chart. In Japan, over 20,000 copies sold in the opening week, with the set entering the Oricon charts at number 10.
Mono Masters compiles the mono mixes of Beatles singles, B-sides, and EP tracks that did not appear on any of the UK albums or Magical Mystery Tour. It includes previously unavailable true mono mixes of four Yellow Submarine songs: Only a Northern Song, All Together Now, Hey Bulldog, and It's All Too Much.