Short answers, pulled from the story.
The name came from a Manchester publican who noticed a resemblance between lead singer Peter Noone and Sherman, a character from the Rocky and Bullwinkle cartoons. Sherman was shortened to Herman, and the group became Herman and His Hermits, which was soon contracted to Herman's Hermits.
Their two US number one singles were "Mrs. Brown, You've Got a Lovely Daughter" and "I'm Henry VIII, I Am". Between March and August 1965, the group had twenty-four consecutive weeks in the Billboard Hot 100 Top Ten across five singles. Billboard magazine ranked them America's top singles act of 1965, ahead of the Beatles.
All of Herman's Hermits' major hits were produced by Mickie Most, an independent producer who worked with EMI. Most recruited session musicians including Jimmy Page and John Paul Jones for many recordings, a practice that caused lasting tension with the band members.
Noone left to pursue a solo career in 1971, officially departing on his 24th birthday after the group went out to dinner and agreed to call it a day. He later reflected that during his time with the Hermits, he had repeatedly prioritized the group's financial security over his own individual opportunities.
Barry Whitwam and Peter Noone have disputed ownership of the Herman's Hermits name since the 2000s. Whitwam registered the name in Australia in 2004 and later in the UK and Europe. A 2009 US tour ended in litigation over misleading advertising, after which Whitwam stopped touring in America. Noone continues to perform as "Herman's Hermits Starring Peter Noone."
The group played on all three of their number one hits and most of their US Top Ten singles, though Mickie Most also used session musicians on some tracks, as was standard industry practice at the time. Noone later stated that as the schedule intensified, he and Most made decisions that excluded the other Hermits from recording sessions.