Short answers, pulled from the story.
Square sent a letter to customers in 1987 regarding an abandoned Famicom Disk System project titled The Emergence of Excalibur. This abandoned project used the Seiken Densetsu trademark which Square had registered in 1989 before reusing it for a Game Boy action role-playing game in 1991.
Koichi Ishii directed the new game that began as Gemma Knights and was renamed Final Fantasy Adventure for its North American release. He viewed the Mana series not as a collection of video games but as a fictional world illustrated through them while drawing inspiration from abstract images of his childhood memories.
A five-volume manga based on Legend of Mana drew by Shiro Amano and published in Japan by Enterbrain ran between 2000 and 2002. An adaptation drawn by authors led by Shiro Amano appeared two days later on the 25th of February 2004 following the initial publication.
The series has sold over 8 million copies by 2021 according to available sales data. By March 2011, series titles had already sold over 6 million units with Secret of Mana shipping over 1.83 million copies worldwide.
Yoko Shimomura composed the score for Legend of Mana which she considered her best self-expression among all compositions. Hiroki Kikuta composed the scores for Secret of Mana and Trials of Mana while Kenji Ito returned with Sword of Mana composing roughly one third of the Children of Mana soundtrack.