This goes for Europe and North America.
Directly to you from Twitter:
Excited for #PokemonCrystal? It’s now available for pre-purchase! Head over to Nintendo eShop with your #3DS family system and be ready to play when the game launches 1/26! https://t.co/UpNH4wGXtj pic.twitter.com/s0Qtq3nkGk— Nintendo of America (@NintendoAmerica) January 12, 2018
…Wanna play? Buy a 3DS.
And if you’ve already got yours, here are all the games already available on the platform. 😀