Short answers, pulled from the story.
Rio de Janeiro was founded on the 1st of March 1565 by the Portuguese, led by Estácio de Sá. It was named São Sebastião do Rio de Janeiro in honor of Saint Sebastian, the patron saint of Portugal's reigning monarch Sebastião.
Portuguese sailors who entered Guanabara Bay on the 1st of January 1502 mistook the broad bay for the mouth of a river, calling it the January River. The name Rio de Janeiro means "January River" and derives from that initial misidentification.
Napoleon's invasion of Portugal in 1808 forced the Portuguese royal family, Queen Maria I, and most of Lisbon's nobility to flee across the Atlantic. Rio de Janeiro became the seat of the court and functioned as the capital of a European monarchy operating from one of its colonies, one of the few times in history such a transfer occurred.
Valongo Wharf was the main slave-landing point in Rio de Janeiro. Between 1811 and 1831, between 500,000 and a million enslaved people arrived there, making the Port of Rio de Janeiro the largest slave port in the Americas. The site is now a UNESCO World Heritage Site.
Rio de Janeiro ceased to be Brazil's capital on the 21st of April 1960, when the seat of government was officially transferred to the newly built Brasília. Rio had served as capital since 1763, first as a colonial capital and then as seat of the empire and republic.
Rio de Janeiro hosted the 2016 Summer Olympics and Paralympics, becoming the first South American and first Portuguese-speaking city to hold the Games. The Maracanã Stadium hosted the finals of the 1950 and 2014 FIFA World Cups, and the city also held the XV Pan American Games in 2007 and the G20 summit in 2024. Rio is scheduled to host the FIFA Women's World Cup in 2027.