^^^^ Spoken like someone who has no clue about bootlegging.
As others have said, you probably have a bootleg. People often mix up bootlegs with fan-made hack games and assume any bootlegged Pokemon game is one of those. What it often means is that a bootlegger somewhere in Asia or Africa produced a game cart with the actual Pokemon game on it. For the most part, it should function just fine within (in your case) a GBA or DS GBA slot just like a normal game.
The main exceptions are in terms of interacting with other games and lifespan of the cart. Bootlegged games have varying degrees of success of being able to battle/trade or transfer from 3->4, but most of them won't be able to at all.
Also the carts tend to wear out as yours seems to be doing now.
The only 100% surefire way to never get a bootlegged Pokemon game is to purchase it yourself from traditional retailers, preferably at their physical retail store. Do not assume that just because it is a big chain, it wouldn't have bootlegged games. I've purchased bootlegged vinyl records from major chains before and have found bootlegged GBA Pokemon games at pawn shops and Game Stop's used games section. At least with major retailers, you'll be able to return for a refund.
My guess is that your non-gaming parent or aunt or whatever went to a Gamestop and purchased a used copy because it was $5-10 less than the new and that's how you got a bootleg. Since it has probably been several years since purchasing it, you have no real chance of returning it.
You can probably do a Google search to verify this. I believe GameFAQs has guides in their GBA section on how to detect bootleggs, and I'm sure other sites do too.