Short answers, pulled from the story.
By 1994, an estimated 25 million people in the United States alone had played Street Fighter II, across arcades and home consoles. Worldwide, more than 200,000 arcade cabinets and 15 million software units of every version had been sold.
Street Fighter II was designed by Yoshiki Okamoto and Akira Yasuda, with Akira Nishitani also in charge of game design and Noritaka Funamizu serving as producer. The two lead designers had previously worked together on the arcade game Final Fight.
Capcom rotated the names of the three Shadaloo Bosses when localizing Street Fighter II for overseas markets. The boxer, originally named M. Bison (short for Mike Bison, a pastiche of Mike Tyson), was renamed Balrog internationally to avoid a potential likeness infringement lawsuit. The names of Vega and M. Bison were reassigned accordingly.
The combo system was discovered by accident during a bug check in the car-smashing bonus stage. A developer noticed that a sequence of punches could chain into additional hits; the team recorded the sequence on tape and, finding the timing too difficult for most players, left it in as a hidden feature. It later became a defining mechanic of the fighting game genre.
Yoko Shimomura composed the vast majority of the in-game music for Street Fighter II. She left Capcom for Square two years after the game's release, making it the only game in the Street Fighter series on which she worked. Isao Abe, a Capcom newcomer, composed a few additional tracks and went on to become the main composer for subsequent Street Fighter II versions.
Street Fighter II was the best-selling fighting game with 15.5 million units sold across all versions and platforms, a record it held until Super Smash Bros. Ultimate surpassed it in 2019. Guinness World Records awarded it the titles of First Fighting Game to Use Combos, Most Cloned Fighting Game, and Biggest-Selling Coin-Operated Fighting Game in its 2008 Gamer's Edition.