In order to play the stage, the player needs to have completed the Sonic Episode in regular gameplay. Once cleared, the Sonic Boss Attack can be selected in the Episode Select. Any Level Up Items and Gems obtained in the Sonic Episode can be used for this level.
The objective in this level is for the player to defeat the boss or all waves of enemies in each section to progress through the stage. In sections where the player has to defeat the boss, the enemies that spawn are optional for the player to defeat for bonus points. Any Rings obtained are carried over to the next section.
The first section of the level is the battle against the Egg-Cerberus where the fight is nearly identical to the regular boss fight, except for the presence of enemies that spawn in the arena where defeating them is optional. Enemies that spawn here include Egg Bombers, Egg Chasers, Egg Commanders, Egg Liners, Egg Rounders and Egg Sweepers. The Egg-Ceberus' attack behavior is slightly different in this level, being able to shake Sonic off even if he grabs onto the antenna for the first time. Once the Egg-Ceberus is defeated, the player proceeds to the next section.
The second section of the level is an enemy wave attack and it takes place in White Acropolis, where Shadow and Silver would normally fight their versions of the Egg-Ceberus and Egg-Genesis respectively. After a wave of enemies is destroyed, the next group of enemies will spawn. Enemies that spawn here include Egg Commanders, Egg Keepers, Egg Liners, Egg Rounders, Egg Gunners, Egg Stingers, Egg Sweepers, Egg Guardians and Egg Flyers. The player will need to use the Pulley and jump off it to defeat airborne enemies, or enemies standing on the elevated platforms located here. There are Ring Bonus Item Boxes up in the air or behind rocks for the player to use if they are running low on Rings. Once all enemies are defeated, the player is able to proceed to the next section.
In the third section, the player simply battles against Silver the Hedgehog without any additional enemies and his attack pattern remains unchanged from the regular boss fight. Once Silver is defeated, the player can move on to the next section.
The battle takes place in the future timeline at the area where Shadow normally fights Mephiles Phase 1 although instead of fighting Mephiles, the player fights wave of enemies. Fitting the scene, the only enemies the player will encounter here are Iblis's Minions, namely Iblis Biters, Iblis Takers, Golems, Iblis Worms, Gazers, Stalkers, Trickers and Titans (the latter half which are encountered by Sonic in this stage exclusively). Over the edge of the arena, there are several Iblis Takers which do not have to be defeated but the player can use Homing Attacks on them to obtain a Ring Bonus Item Box. The player proceeds to the next section once all waves of enemies have being cleared.
The next fight in this section is against Iblis in his second phase. The arena now spawns less Rings on the platforms although just like in the previous section, the player can use the Iblis Takers that spawn in this stage as Homing Attack targets to reach Ring Bonus Item Boxes. Attack-pattern wise, Iblis behaves slightly different compared to the original fight, but otherwise uses the same attacks. Once Iblis is defeated, the player can move onto the next section.
The Egg-Genesis is the main boss in the next section along with optional waves of enemies to defeat including Egg Gunners, Egg Cannons, Egg Stingers and Egg Lancers and the Gunner variant of the Egg Busters. The Egg-Genesis can now fire its charged shots from the beginning of the fight but otherwise it remains exactly the same in its regular boss fight. After defeating it, the player can proceed to the next section of the stage.
The next section occurs at the Forest albeit only an enemy attack section consisting waves of previous Eggman robot enemies but with Egg Searchers, Egg Hunters and the rarely-seen Egg Keepers added to the mix. Once all enemies have been destroyed, the player can move onto the final section.
In the last section of the level, the player battles the Egg-Wyvern, although additional Egg Gunners will also attack. Otherwise, this fight is exactly the same as it was in the original boss fight. Defeating it will end the level.