The following lists consist of removed content previously shown in a demo before being scrapped or altered from its original implementation. Note that normal attacks are too numerous to list due to being changed constantly; as such, they will not be mentioned below.
Lloyd had a set of techniques called "Linked Artes" in versions 0.8a and 0.8b. These techniques allowed Lloyd to instantly cancel certain moves into into each other in rapid succession. They were removed in v0.9a, as they were found unnecessary.
Beast replaced Sonic Thrust as Lloyd's side special move in demo v0.5a only for Sonic Thrust to be brought back in demo v0.6 and Beast to be relocated to Lloyd's forward smash. Sonic Thrust then became Lloyd's dash attack, as Tempest replaced Sonic Thrust as his side special move.
Sora's special moves were changed multiple times. In v0.6, his down special move was Magic Swap. It got replaced by Thundaga on v0.8b, which, in turn, was replaced by Command Deck in Beta.
When Thundaga replaced Magic Swap, Blizzard (part of the move) became his back throw, while Firaga (also part of the move) became his standard special move. Command Deck, however, made all three spells part of it.
Strike Raid, in v0.9b, was moved from Sora's side special to his standard special, to accomodate Flowmotion.
Bandana Dee and PAC-MAN were both removed as Assist Trophies in Beta, due to their new roles as playable characters.
Amigo was removed as an Assist Trophy in Beta, due to being never fully functional and because his music never picked up where it left off.
Renji Abarai was replaced with Rukia Kuchiki as an Assist Trophy in Beta, due to being excessively buggy with floor collisions, teleporting around, and slippery movement.
Light Yagami was removed as an Assist Trophy in Beta, due to being "completely overpowered" and originating from an anime franchise with no other representation in Super Smash Flash 2.
MissingNo. was removed as a Poké Ball in Beta, due to its function being deemed redundant, along with reports of having scared users playing in fullscreen mode into mistakenly thinking that their computers had actually crashed.
Link was given completely custom sprites for v0.9b. He was later recolored to match his color scheme in Super Smash Bros for Nintendo 3DS and Wii U.
Naruto had his color scheme altered in a patch for v0.9a. Goku and Ichigo received the same treatment in v0.9b, while Pikachu and Lloyd were changed in Beta. The latter also had a correction of his swords, preventing him from flipping his swords based on the direction he faces.
Multiple characters, most notably Tails, got minor tweaks to their color scheme in Beta 1.2.
Temple has received multiple sprite changes from demo to demo.
Waiting Room got a complete overhaul from v0.8b to v0.9a, but then was altered again from 0.9b to Beta; in v0.9b, its sides were walls extending to the lower blast zone. In Beta, it was given slopes on its underside similar to the original Online Practice Stage.
Activating the Smash Ball to perform a Final Smash was originally much different. Players would have to pick it up from the ground and activate it by shielding and then pressing the standard special move button.
The command to use a Final Smash changed to simply pressing the standard special move button in v0.2a, but it would not be until v0.2b that the Smash Ball is a floating item rather than one players can pick up.
Lakitu originally had a much different function as an Assist Trophy, following the player who summoned it and catching it with a fishing rod if it fell off-stage. As of Beta, Lakitu now floats high across the stage and drops Spinies drop down that will attack opponents they make contact with.
SSF2's first logo by E.Laimo, used in v0.6.
SSF2's second logo by Neron, used from v0.7 to v0.9b.