It's a cheatcode. You're using a device outside of the game to get 99 lives.
Under competition rules:
* Gamesharks, similar cheat devices, "turbo" or "autofire" features of controllers, and ROM save states must not be used, nor any functions on the emulator, such as slowing down the speed of the game.
* The original game and all its contents must be preserved and unmodified.
I don't know under what of those rules it would count, but surely, it's probably not allowed to use that code for competition, judging from these rules.