Credits: ArathNidoGamer
You can become one of many characters that had an appearance in the original games. Not only will you look like them, but you will also inherit some of their features. Those characters are unlockable by buying skins from Cream the Rabbit NPC. The trader is bound to a new biome called Green Hill Zone, which mirrors one of the levels from the game.
When you wear a Sonic skin, your sprint makes the character spin and run at an enormous speed. Jumping capabilities also will be severely increased. In Tails' skin, you can fly even if you press the crouch button.
Metal Sonic is one of two bosses you're going to be dealing with. Defeat him, and you'll get a Blue chaos emerald.
Fight with Eggman to receive Gray Chaos Emerald and Eggman's Drill.
Collect all eight emeralds and combine them together to become Super Sonic. Check out also this Sonic-style map, which will be great for testing out your new powers.
Edited: 25.01.24
Reason: Cosmo Sonic (Christmas cheer), Amy, Rattlesnake, Sonic Classic added