To net this achievement you must complete each act of all four levels as Super Sonic. What this means is that you must BE Super Sonic as you cross the goal post in all action stages (NOT boss stages: this means Spash Hill Zone Acts 1-3, Casino Street Zone Acts 1-3, Lost Labyrinth Zone Acts 1-3, and Mad Gear Zone Acts 1-3). If you are Super Sonic in the level but change back because you run out of rings before you cross the goal post, this will not net you the achievement.
In order to do this you need to have received the "Super Sonic Genesis" Achievement already. Refer to the solution for this achievement for details. To activate Super Sonic press X after grabbing 50 or more rings.
It is a good idea to go for this achievement alongside "Contender"--you need to have completed all the Special Stages anyways for Contender--which would unlock the ability to become Super Sonic for you anyways.
Tough Levels:
This really is an easy achievement except there are about 2 levels that are annoying--Lost Labyrinth Act 1 and Casino Street Act 2. Just make note that in Casino Street, the large gaps at the end with the flipping cards CANNOT be jumped in one shot as Super Sonic, and in Lost Labyrinth Act 1 you have to ride the last bounder all the way to the end--Super Sonic can't make that huge jump.
Useful tools:
-You will know you completed the act as super sonic if you have the super sonic logo displayed when your completion time is given.
-It is quite possible (but not as fun) to just complete the level as regular sonic with all your rings and then just activate Super Sonic before you cross the goal post.
-If you look at the leaderboards you can see what levels you have completed as super sonic by seeing if you have a Super Sonic completion time/score. Go to either time attack or score attack and choose my times/scores and then press "Y" until only the super sonic times/scores are displayed. If you have a time/score listed then you have that level completed.
If you have questions ask!