If you've seen a download claiming to be Pokémon Scarlet for GBA , it's almost certainly a (like Pokémon Scarlet GBA by a modder named NintendoBro or similar), not an official Nintendo game. These are unauthorized, often buggy, and could contain malware if downloaded from sketchy sites.
I notice you're asking about a — just a quick heads-up: there is no official Pokémon Scarlet or Violet version for the Game Boy Advance . pokemon scarlet gba download