Sonic & Knuckles

Pretty simple especially if your familiar with the process of obtaining Chaos Emeralds in Sonic 3, all you need to do is collect 1 Chaos Emerald.

Scattered across pretty much every level there are giant golden rings that, when touched, warp you to a 3D special stage - the aim is to collect every blue sphere and avoid the red ones - collecting a blue sphere will turn it into a red one behind you - however collecting a rectangle of blue ones will cause them all to turn into rings which you may collect if you wish.

The amount of spheres left to collect is displayed in the top left corner and once every blue sphere is obtained you are rewarded with an Emerald.

If you are struggling for whatever reason - use the save anywhere feature on the pause menu before the round so if you mess up just re-load your save and try again - once you fail a special stage it no longer allows you to access that stage again through the same ring.

Just to clarify you can only get this achievement by playing the standard Sonic and Knuckles game - not the bonus Sonic 3 and Knuckles game.

Notice that the picture of this achievement was used in Sonic The Hedgehog 3 for completing the Ice Cap Zone?

The Special Stages are the exact same as Sonic The Hedgehog 3. However since this game is set straight after the events from Sonic The Hedgehog 3, the difficulty of these Special Stages is slightly harder. The newest features included is the Yellow Ball which is a Spring. The spring makes you bounce from one end of the arena to the other. But it may put you out of control for a brief moment so be careful.

Throughout all the levels you play, there are secret areas which contain Giant Rings which spin round in circles. Find a ring and jump inside it to begin a Chaos Emerald Mini-Game.

You will then be placed in a 3D View, and your goal will be to run around the arena and grab the Blue Spheres, whilst avoiding the red ones. Touching the red ones will eliminate you and will return you to the level you are playing in.
Each time you touch a Blue Sphere, it will turn from blue to red. Successfully grab all of the blue spheres, and you will win a Chaos Emerald and the achievement.

You can earn rings in a special stage zone by finding a collection spheres of more than 4 and then running around the outer blue spheres, blocking the inside ones making a red sphere square.
Once you've turned the last sphere in the square to red, all the spheres in that particular location will turn into rings, which will give you extra points. The rings obtained in a special stage zone will not transfer to the level you are playing in. They will be used as points.

Additionally if you successfully grab all the rings in a Special Stage Zone that are available, you will be awarded "Perfect" which will give you 50,000 Points, which is an extra life in the main game.

Note: Be careful if your trying to turn the spheres into rings. If you go too far inside the square, or go off-course you may lead yourself to an area full of red spheres, and a trap.

Note: You can jump in a Special Stage as well by pressing the Jump Button. You will need to use this move when you do the harder challenges.

Note: The longer you last in the arena, and the more spheres you grab, the faster the music and the arena goes, so you need to watch yourself when the speed increases.