Short answers, pulled from the story.
Square was initially established in September 1983 as a software subsidiary of Den-Yu-Sha, an electric power conglomerate. It was re-established as an independent developer in September 1986 with capital of 10 million yen.
Square was founded by Masafumi Miyamoto, who spun off the computer game software division of Den-Yu-Sha, a power line construction company owned by his father Kuniichi Miyamoto. Hironobu Sakaguchi and Hisashi Suzuki were among the earliest hires.
Final Fantasy was released in 1987 and sold over 400,000 copies in Japan. When it launched in North America in 1989, it sold 700,000 copies.
Square left Nintendo in the mid-1990s because CD-ROM distribution on Sony's PlayStation was far cheaper than Nintendo's continued use of expensive ROM cartridges. One Square employee recalled Nintendo telling the company to "never come back" after the split.
The commercial failure of the 2001 film Final Fantasy: The Spirits Within, which cost US$137 million to produce but grossed only $85 million, caused Square's first-ever financial loss and disrupted initial merger talks. After the success of Final Fantasy X and Kingdom Hearts, negotiations resumed and Square Enix was formed on the 1st of April 2003.
Square Pictures was closed following the film's box-office failure in 2001. Its staff and assets were merged into Square Visual Works, though the Hawaiian branch later produced the CGI short Final Flight of the Osiris before shutting down in 2002.