Short answers, pulled from the story.
Tasha's Cauldron of Everything arrived on the shelves of local game stores and online retailers on the 17th of November 2020. Wizards of the Coast released an exclusive edition with white foil alternate art covers by Joy Ang through their local game store program in January 2022.
Magali Villeneuve designed the standard cover art that greeted players who bought the book from major chains. Local game store customers received a different version with artwork by Wylie Beckert, while Wizards of the Coast released an exclusive edition featuring white foil alternate art covers by Joy Ang.
The first chapter of the sourcebook introduced twenty-six new subclasses for existing character classes including three options for the Artificer class drawn from Eberron: Rising from the Last War. Players could choose two or three options for each of the twelve previously existing classes to customize their characters.
A significant portion of the text focused on optional rules that decoupled race from mechanical abilities allowing players to adjust features and ability modifiers traditionally tied to species. Jeremy Crawford explained that racial ability score increases existed strictly to reinforce archetypes dating back to the 1970s rather than for game balance purposes.
The third chapter cataloged twenty-one spells including three attributed directly to Tasha and writers introduced thirty-six magic items for players to discover during campaigns. A new type of wondrous item called magic tattoos appeared in this supplement with eleven magical tattoo entries filling out the list of these new objects.