You may only get ONE Chaos Emerald per Act, so if you get the Red Emerald in Sylvania Castle Zone Act 1, then you can no longer get Chaos Emeralds in Sylvania Castle Zone Act 1. You must use this wisely to pass Special Stage 7. While this is active any ring that touches Sonic, Tails, OR the String, is collected. In some Stages you may find Tag Badges, these will tie Sonic and Tails together with a String of sorts. In each Stage you may find Bombs that will cause you to lose a large amount of rings if you touch one. In each Stage you may find Green electrical barriers the will stun you and slow you down. But if you do not move fast enough they will disappear.

If you collect them all you will receive a bonus amount of rings. In each Stage you may find Timed Rings, A set amount will show up on the screen and those are the ONLY rings in the area. You can use X button to make Sonic and Tails Boost at higher speeds if you need to move faster.

If you do not get the required amount of rings before passing any of the 3 barriers, you will fail the Special Stage. Once inside you will be asked to get a certain amount of rings, get the amount requested and you will be given a 2nd amount of rings, get them once again and you will be given a 3rd amount of rings, after getting this 3rd amount you will receive your Chaos Emerald. To get to a Special Stage, you must collect 50 Rings in Act's 1,2, or 3 of a Zone and pass the goal flag at the end of the Act, here you will notice a Giant Ring floating in the air, jump inside it to go to the Special Stage. There are 7 Chaos Emeralds in the game (like there are in every Sonic game) to get to each you must play in a Special Stage and win. All Chaos Emeralds Found! - 30G (Original Achievement)

Sonic windows zone act 1