The Time Attack mode could consist of completing an act of the game with the following alterations (technically, act-specific scripts should take care of these alterations, the GMS rooms should not be changed):
Giant Rings, checkpoints, and Time Posts are completely absent.
AAZ Act 1 ends with its act end panel. VVZ Act 1 also ends without battling Metal Sonic, the fake act end panel being the real one instead..
Acts 2 don’t have bosses: the Time Attack scripts should place act end panels and limit camera movements accordingly.
Acts that have intro cutscenes or mini-acts (AAZ act 1 Future with the Tornado, DDZ act 1 with the VVZ transition) skip those.
The cutscene in the middle of SSZ is replaced with a portal like in FFZ.
Losing a life makes the player forfeit the challenge.
The Time Attack mode could consist of completing an act of the game with the following alterations (technically, act-specific scripts should take care of these alterations, the GMS rooms should not be changed):
Losing a life makes the player forfeit the challenge.