Requiring victory to leapfrog their opponents and finish second behind Senegal, Guinea-Bissau opened the scoring in first-half stoppage time through Piqueti.
Frédéric Mendy doubled the lead after 73 minutes and Jorginho launched the celebrations 10 minutes from time with his side’s third.
It was a remarkable turnaround for Baciro Cande’s men.
Return
After winning their opening Group I match against Eswatini on 13 November 2019, Guinea Bissau lost to Congo 3-0 four days later and then suffered successive defeats away and at home to Senegal to lie third with three points, four adrift of second-placed Congo.
But a 3-1 win in Eswatini on 26 March coupled with a 0-0 draw between Congo and Senegal brought Congo within range before Tuesday's pyrotechnics at the 24 September Stadium.
In Group E, Mauritania secured a spot at the finals in Cameroon next January following a 1-0 victory in Central African Republic.
Aboubakar Kamara got the winner on the stroke of half-time to take the nation back to the tournament where they made their debut in 2019.
Mauritania’s sports minister Taleb Sid'Ahmed led the tributes.
“Congratulations to the valiant team for their qualification to the final phase of the CAN 2021,” he tweeted.
“This victory is an honour for our country which is now part of the great nations of sport.”
Félicitations aux vaillants Mourabitounes pour leur qualification à la phase finale de la CAN 2021 . Cette victoire est un honneur pour notre pays qui fait désormais partie des grandes nations du sport.
— Taleb Sid'Ahmed (@TalebSidAhmedMr) March 30, 2021
The Mauritanian football federation added: “Mauritania will be at the party in Cameroon in 2022.”
#FFRIM 🔝 La Mauritanie 🇲🇷 sera de la fête au Cameroun en 2022 🙈🙊🙉 pic.twitter.com/np5Et5H3Ur
— FFRIM (@ffrim) March 30, 2021
Cape Verde, who reached the quarter-finals during their first appearance at the competition in South Africa in 2013, returned after missing out in 2017 and 2019.
They edged past Mozambique 1-0 courtesy of a Faisal Bangal own goal just after half-time.
The victory took them onto 10 points. Rwanda, who could have overtaken them if Mozambique had won, drew 0-0 with Cameroon who claimed Group F with 11 points.
