Short answers, pulled from the story.
Gary Gygax wrote the original Unearthed Arcana book to raise money for TSR because the company was deeply in debt when he began work on the project. He announced the release of this supplement in the March 1985 issue of Dragon magazine and planned for the book to arrive during the summer of that same year.
Wizards of the Coast released a premium edition on the 19th of February 2013 featuring gilded pages. This specific printing became the first version to include all previously published errata directly in the corrected text after errata were never incorporated into later printings of the manual itself.
Andy Collins, Jesse Decker, David Noonan, and Rich Redman wrote the supplement titled Unearthed Arcana for Dungeons & Dragons third edition which arrived in February 2004. The designers targeted experienced players and Dungeon Masters seeking customization options while explicitly avoiding replicating the mechanical structure of the original book.
The title Unearthed Arcana began appearing as a semi-regular series of digital releases on the official D&D website starting in February 2015 to present work-in-progress content such as class archetypes and rule variants. All remaining content received archive status on the 12th of August 2021 before the series returned in December 2024 following the 2024 revision of fifth edition.
Paul Cockburn reviewed the original Unearthed Arcana in issue 73 of White Dwarf magazine published in January 1986 and rated the book four out of ten overall calling it a rules extension package adding very little interest or value. He concluded that the new classes were overly powerful according to Lawrence Schick's notes in his 1991 book Heroic Worlds.