Short answers, pulled from the story.
The Nintendo 3DS version launched in Japan on the 13th of September 2014, and in North America and Europe on the 3rd of October 2014. The Wii U version released in North America on the 21st of November 2014, with Japan receiving it last on the 6th of December 2014.
The games were developed jointly by Bandai Namco Studios and Sora Ltd., with series creator Masahiro Sakurai leading development. Staff members from Bandai Namco's Soulcalibur and Tekken teams assisted Sakurai, and additional support came from companies including tri-Crescendo.
The Wii U version sold 5.38 million copies worldwide by September 2022. At launch, it became the fastest-selling Wii U game in the United States, with 490,000 physical and digital copies sold in its first three days, surpassing the record previously held by Mario Kart 8.
Bayonetta won the ballot among characters Sakurai described as negotiable and realizable, ranking first in Europe and in the top five in North America. The two overall top vote-getters were Sora from Kingdom Hearts and Banjo and Kazooie from the Banjo-Kazooie series, but Sakurai did not reveal this until October 2021.
The Ice Climbers were removed due to technical limitations of the Nintendo 3DS hardware, which could not handle the synchronized artificial intelligence required for the pair. Hardware constraints also led to the removal of mid-match character transformations and the lack of Circle Pad Pro support.
Seven DLC characters were released between April 2015 and February 2016: Mewtwo, Roy, Lucas, Ryu, Cloud Strife from Final Fantasy VII, Corrin, and Bayonetta. The DLC became unavailable to purchase after the Nintendo eShop for 3DS and Wii U closed in March 2023.