Sonic Adventure

To unlock the Sonic the Hedgehog achievement you have to beat all 10 action stages and boss battles in the Sonic the Hedgehog Storyline
The action stages and boss battles in order are:

Chaos 0: Station Square
#1 Emerald Coast: Station Square
Egg Hornet: Mythic Ruins

#2 Windy Valley: Mythic Ruins
#3 Casinopolis: Station Square
#4 Ice Cap: Mythic Ruins
Knuckles and Chaos 4: Mythic Ruins

#5 Twinkle Park: Stations Square
#6 Speed Highway: Station Square
#7 Red Mountain: Mythic Ruins
#8 Sky Deck: Egg Carrier

E-102 "y" and Chaos 6: Egg Carrier
#9 Lost World: Mythic Ruins
#10 Final Egg: Mythic Ruins/Egg Carrier
Egg Hornet: Mythic Ruins/Egg Carrier
Complete Achievement Unlocked!

Throughout the game you will acquire some abilities to benefit your character. Some of them require you to have while other will be there to help. Here is the list of Sonic's abilities and where to find them:

Light Speed Shoes: Allows you to "dash through rings" Must have item found after you beat Windy Valley. Located in Station Square in the sewer area.

Crystal Ring: "Decreases the time needed to dash through rings" Optional item located in the hotel room of Station Square. Must use light speed dash in order to acquire.

Ancient Light: "Allows you to attack enemies using the Light Speed Shoe ability" Must have weapon found right before you enter the action stage Red Mountain. Located on the rock near the bridge to the Master Emerald Shrine.

Hopefully this will be of great help to all you guys! ^_^ Please message me if you need any more help!