Short answers, pulled from the story.
Five people including John Carmack, Tom Hall, Adrian Carmack, Kevin Cloud, John Romero, and Dave Taylor began work on Doom in November 1992 at Suite 666. The team developed the game under the working title Green and Pissed before renaming it to Doom based on a line from the 1986 film The Color of Money.
The first episode of Doom uploaded to the internet at midnight on the 10th of December 1993 after thirty straight hours of testing. Ten thousand people attempted downloads simultaneously causing network congestion that led university networks to ban multiplayer games within hours.
Doom became notorious for its high levels of graphic violence and satanic imagery generating controversy from broad groups worldwide. In Germany the game was classified as harmful to minors by the Federal Department for Media Harmful to Young Persons until rescinded in 2011. Eric Harris and Dylan Klebold were found to be avid players before committing the Columbine High School massacre on the 20th of April 1999 sparking renewed debate about causation.
All versions combined sold 3.5 million copies by the end of 1999 while an estimated six million people played the shareware version by 2002. By late 1995 Doom was estimated installed on more computers worldwide than Microsoft's Windows 95 operating system.
Student Brendon Wyber led creation of the first full level editor called the Doom Editor Utility on the 26th of January 1994. Greg Lewis released DeHackEd patch editor later in 1994 allowing editing of the game engine itself.