Short answers, pulled from the story.
Gary Gygax created the first Dungeons & Dragons rules in 1974 with a production budget of just $2000. He pressed local friends including Cookie Corey, Greg Bell, Dave Arneson, Keenan Powell, and Don Kaye into service to create illustrations because he could not afford professional artists.
TSR split the original D&D line into two distinct branches in July 1977. John Eric Holmes edited the Basic Set as an introductory version for beginners while Gary Gygax developed Advanced Dungeons & Dragons simultaneously as a more complex system between 1977 and 1979.
Advanced Dungeons & Dragons 2nd Edition arrived in 1989 after two years of development led by David Zeb Cook. This edition removed certain controversial elements like demons and devils renaming them tanar'ri and baatezu instead while character classes such as assassin and half-orc disappeared from official play.
Pathfinder Roleplaying Game emerged as best-selling alternative in 2009 backward compatible with D&D v3.5 due to anger among players following Fourth Edition announcement. Slashdot reported anger among players and retailers following Fourth Edition announcement due to financial investment in version 3.5 so many chose continuing older editions or switching games like Pathfinder published by Paizo Publishing.
Public playtesting began the 24th of May 2012 with final packet released the 20th of September 2013. Basic Rules free PDF arrived the 3rd of July 2014 while Starter Set launched July 15 featuring Lost Mine of Phandelver module before Player's Handbook hit shelves the 19th of August 2014.