Theres this ring glitch that you can do so you can get a bunch of rings.
Its a strange glitch, but I'll explain below.
Spoiler:
This is how you multiply rings. First, you will need a very expensive item. Be sure you save it into your Chao Garden. Now, go to the Black Market and sell the item. Press the reset button. When you go to the Stage Select, you will see your rings have stayed the same. If you go back to the garden where the item was, then its still there. Anyways, this happens because when you restart it saves your ring data but not your chao data. So that's the reason you save the item into your Chao Garden. So it won't be gone forever.
City Escape Mission 3 is another way, by getting as much rings as possible, going to the Restart ring, and repeating before, until you have 999 rings. Then I complete the level.
But I find this to take longer.
Last edited by FastRunningChao on Thu Jan 30, 2014 9:18 pm, edited 1 time in total.
There are enough normal ways to get huge numbers of rings in SA2B (like just drawing out the boss fight with Sonic or Shadow) that I don't really bother with tricks or anything. On SADX though, I use Gamma and the button in the hotel to amass rings and then clear Emerald Coast. This can be even faster than selling items back to the Black Market.