For the record and future updates of this quiz: CBF (Brazilian Football Confederation) has reconized at August 25th the 1937 Champions Tournament as the first Brazilian National League, which Atlético Mineiro has won.
here's a link to the reference about it: https://www.cnnbrasil.com.br/esportes/cbf-reconhece-titulo-brasileiro-do-atletico-mg-em-1937-clube-agora-e-tricampeao/
According to Brazilian justice, Sport is the only champion of 1987. In the future they might consider both, but for now, Flamengo is not considered the 1987 champion.
here's the article from the STF's website: https://noticias.stf.jus.br/postsnoticias/stf-mantem-sport-como-unico-campeao-brasileiro-de-futebol-de-1987/
here's a link to the reference about it: https://www.cnnbrasil.com.br/esportes/cbf-reconhece-titulo-brasileiro-do-atletico-mg-em-1937-clube-agora-e-tricampeao/
here's the article from the STF's website: https://noticias.stf.jus.br/postsnoticias/stf-mantem-sport-como-unico-campeao-brasileiro-de-futebol-de-1987/