The normal Infinite Rings codes in Shadow the Hedgehog break the Circus Park level, where the Hero Mission requires collecting 400 Rings. Since they're set to 999, the level autocompletes and then loops. Changing the 999 value doesn't work either, since the value would still be stuck at whatever is specified, so the mission couldn't be completed. Instead I've made a code that sets the minimum number of Rings to 20, so you can never drop below 20 Rings, but you can still collect more.
The AR code below is for the US release (GUPE8P), but it should be trivial to modify this to work with other regions if there's a normal Infinite Rings AR code in those regions.
The AR code below is for the US release (GUPE8P), but it should be trivial to modify this to work with other regions if there's a normal Infinite Rings AR code in those regions.
Code:
$Always At Least 20 Rings P1
2C57670C 00000014
0457670C 00000014