I've been waiting for a TAS of this game, and I liked your run of the last level. But I'm worried that the button combination constitutes a cheat code, which
may not be acceptable as it skips over gameplay and is accessed through the intended manner. See
this rejected submission's judgment message and a discussion on this rule, and
this one which was accepted because the debug menu used was only accessible through a glitch.
I haven't been able to find the M&M's Kart Racing manual online to confirm whether your button combo is an intended code or not; the closest I got was
the DS version publisher's site with a broken link to its game manual. But I just bought a copy of this game from eBay (no fooling, it was cheap too), so in less than a week I can share a scan of the manual and we'll see if it's mentioned.