Short answers, pulled from the story.
Marvel vs. Capcom 3: Fate of Two Worlds was released on the 15th of February 2011 in North America, the 17th of February in Japan, and the 18th of February in Europe, for the PlayStation 3 and Xbox 360.
Capcom confirmed it had shipped more than 2 million copies by the 30th of March 2011, roughly a month and a half after launch. Combined sales of Marvel vs. Capcom 3: Fate of Two Worlds and Ultimate Marvel vs. Capcom 3 across all platforms exceeded 5 million copies.
Ryota Niitsuma produced Marvel vs. Capcom 3: Fate of Two Worlds. He had previously headed production on Tatsunoko vs. Capcom, the game whose three-button control system was carried over into Marvel vs. Capcom 3.
X-Factor is a mechanic that players can activate once per match to temporarily increase their character's damage, speed, and health regeneration. Its duration and power scale upward the fewer active fighters remain on the player's team, giving a last-surviving character significantly stronger boosts.
Comic book writer Frank Tieri was hired to write the character dialogue and the Arcade Mode endings for Marvel vs. Capcom 3. Marvel gave Tieri access to their full library of characters for storyline purposes, which allowed many unplayable characters to appear as cameos.
After The Walt Disney Company acquired Marvel in 2009, Disney chose not to renew Capcom's Marvel license following the release of Ultimate Marvel vs. Capcom 3 for PlayStation Vita in 2012. Both Ultimate Marvel vs. Capcom 3 and Marvel vs. Capcom 2 were removed from Xbox Live Arcade and the PlayStation Network in 2013 as Disney redirected Marvel characters to its own Disney Infinity series.