Nothing major, I just suspect that Sonic & Tails were used, when submissions call for one character only. If this is legit... well, wow. If not, just play again with only one character. Personally, I don't compete in Sonic 2 much anymore, I'm just drawing attention to this for those who do play it.
The "Tails triggers the door" trick was discovered quite a while ago and banned from here, if that's what created this record.
EDIT: The rules have since changed to allow Tails to be controlled by the AI, allowing the strategy in question, but the rest of this topic was made before this change.