Short answers, pulled from the story.
Gary Gygax announced the original Unearthed Arcana book in the March 1985 issue of Dragon magazine with a planned release for the summer of 1985. The 128-page hardback book was written for use with the Advanced Dungeons and Dragons first edition rules and contained new races, classes, and other expansion material.
The original Unearthed Arcana included the barbarian, cavalier, and thief-acrobat character classes along with expansions for the druid and ranger classes. It presented new options for character races such as the drow and svirfneblin and detailed weapon specialization rules for fighters and rangers.
Kim Mohan printed four pages of rules corrections and new supplementary material in the November 1985 issue of Dragon magazine to address the errors found in the book. He also compiled a two-page list of type corrections meant to be pasted into further revisions of Unearthed Arcana.
Wizards of the Coast released a premium edition of the original Unearthed Arcana featuring gilded pages on the 19th of February 2013. This reprint is the first printing of the book to be modified using the errata previously published in Dragon magazine incorporated into the corrected text.
The second book to use the name Unearthed Arcana was written by Andy Collins, Jesse Decker, David Noonan, and Rich Redman. It was published in February 2004 by Wizards of the Coast for use with the Dungeons and Dragons third edition rules.
All remaining Unearthed Arcana content was archived on D&D Beyond on the 12th of August 2021. From August 2022 to November 2023, Unearthed Arcana articles featured One D&D playtest material with releases now exclusive to D&D Beyond in a PDF format.