When performing the Stop 'n' Slam, the user performs an acrobatic maneuver in midair that stops them in mid-flight and makes them plunge straight down on any target below them. How this acrobatic maneuver is executed depends on the user.
In gameplay, this move is useful for reaching targets that appear below the playable characters just as they fly over them while often allowing the player to damage enemies, break weak obstacles and certain platforms, and open Item Boxes in the user's path. In addition, the move will not cancel the momentum the player receives from the Boost Mode. Depending on the user, the Stop 'n' Slam may have other traits to it or be incorporated as another of the user's attacks. However, the move can only be pulled off after the user has been launched into midair by gimmicks like the Spring or Ramp.
Sonic Advance 2
The Stop 'n' Slam maneuvers first appeared in Sonic Advance 2, alongside the other Mid-Air Trick Actions. In this game, the move can be pulled off by any playable character except for Super Sonic. To perform the Stop 'n' Slam in gameplay, the player must press down on and the R Button at the same time after being launched into midair by gimmicks.
Sonic Advance 3
In Sonic Advance 3, the Stop 'n' Slam manuvers can be pulled off by any playable character except Knuckles the Echidna and Super Sonic. Due to the game's partner system, the Stop 'n' Slam can only be used by the characters when they are paired up correctly. As such, Sonic must be paired up with Tails, and Amy must be paired up with Cream (or vice versa), in order for any of these characters to use the Stop 'n' Slam.
Like in Sonic Advance 2, to use the Stop 'n' Slam in gameplay, press down on and the R Button at the same time after being launched into midair by gimmicks.