Round 3 shows the trainee teams as they make their through an interim check at a special venue, rehearsals and a final performance, set on a stage that is larger than they anticipated. The trainees are tasked with completing the 'Seventeen Legendary Mission', covering three songs which they must also self-choreograph. In contrast to other rounds, the 15 trainees learn that the number of &BALLS they receive will be announced live after each performance in the presence of the producers and other trainees.

Round 4 begins and unlike previous missions, they must prepare two performances; one for vocals and one for dance. If they don't get enough &BALLs in this round, the trainees will not be able advance to the final round. The trainees go through practice, interim evaluations and after performing, they discover whether they can completely fill the &RING. At the end, they find out how many members will be in the final lineup. There is an announcement about how the debut group will be decided and a surprise final episode is to be aired live while voting begins.