Short answers, pulled from the story.
Final Fantasy IV is a 1991 role-playing game developed and published by Square for the Super Nintendo Entertainment System. It is the fourth main installment of the Final Fantasy series and follows Cecil Harvey, a dark knight, as he and his allies try to stop the sorcerer Golbez from seizing powerful crystals.
Square titled the game Final Fantasy II in North America because the actual Final Fantasy II and III had never been released outside Japan, and the company wanted to maintain naming continuity. All later localizations reverted to the title Final Fantasy IV after Final Fantasy VII received a worldwide release.
The Active Time Battle system, conceived by Hiroyuki Ito after watching a Formula One race, replaces traditional turn-based combat with real-time speed gauges for each character and monster. Characters act when their individual gauge fills, creating pressure to issue commands quickly. The system was used in five subsequent Final Fantasy games.
The various incarnations of Final Fantasy IV have sold more than four million copies worldwide. The Super Famicom original sold 1.44 million copies in Japan, and the Nintendo DS remake alone sold 1.1 million copies worldwide by May 2009.
Nobuo Uematsu composed the entire score for Final Fantasy IV. The soundtrack includes the track "Theme of Love," which became part of the Japanese school music curriculum. Three official soundtrack albums were released in Japan in 1991 and 1992.
Square significantly reduced the game's difficulty for North American players and removed overt religious references, renaming the spell "Holy" to "White" and the Tower of Prayers to the Tower of Wishes. The changes followed Nintendo of America's censorship policies, which were in place before the ESRB rating system existed.