Short answers, pulled from the story.
QuakeWorld launched on the 13th of December 1996, introducing client-side prediction to improve online play over dial-up connections. Official id Software development ceased with test release version 2.33 on the 21st of December 1998.
Trent Reznor composed ambient soundscapes using synthesized drones to create what he described as sinister, depressive, and frightening audio textures rather than traditional music. He remarked during interviews that the soundtrack included whirling machine noises designed to unsettle players without relying on melodic structures.
The game’s atmosphere drew heavily from H.P. Lovecraft’s Cthulhu Mythos, creating a dark spiritual tone that unsettled players and critics alike. Enemies such as Dimensional Shamblers and Formless Spawn of Tsathoggua appeared throughout the four episodes, each named after elements from Lovecraft’s writings.
Creative differences between Romero and Carmack led to widespread resignations shortly after release including Shawn Green, Jay Wilbur, Sandy Petersen, and Mike Wilson. Romero never received any money from Quake despite leading the project, later releasing Daikatana in 2000 which he considered more enjoyable to make due to reduced interference.
The source code released on the 22nd of December 1999 under GPLv2 allowed fans to create thousands of custom maps still being developed over twenty years later. Team Fortress became the most-played online modification featuring class-based gameplay with restrictions on weapons armor types special abilities granted per character type.