Sonic 3 & Knuckles features several additions to the games not available otherwise, such as small alterations to the levels, and being able to play through Sonic 3 levels as Knuckles, or Sonic & Knuckles levels as Tails, and the ability to save progress in all of the game's levels. Additionally, this was the only way to collect Super Emeralds, w ...Read Morehich are earned by accessing Special Stages in the Sonic & Knuckles levels after collecting all seven Chaos Emeralds from Sonic 3. When all Super Emeralds have been collected, Sonic, Knuckles and Tails can transform into Hyper Sonic, Hyper Knuckles and Super Tails respectively, each with unique abilities.

How long is Sonic the Hedgehog 3 & Knuckles?
When focusing on the main objectives, Sonic the Hedgehog 3 & Knuckles is about 4 Hours in length. If you're a gamer that strives to see all aspects of the game, you are likely to spend around 7½ Hours to obtain 100% completion.