From Sonic Retro
Much like the 2D games, Sonic Heroes has a 2 act and boss structure. Unlike those games, the levels are not named Act 1 and Act 2 but they function in a similar manner. Each set of 2 stages are based around one of the classic Sonic cliches.
The game requires that all 4 teams complete all of the stages and get all 7 Chaos Emeralds before progressing to the Last Story, where all 4 teams participate.