420 is definitely not a funny number in the Netherlands. Except maybe with the permanently online or stoner crowd. I’ve never heard or seen a joke with 420 in the Netherlands. Most people wouldn’t even get what it means and more people would recognize 69 as a funny number than 420.
You can buy a flashcart for the DS and run pirated games on it. So as long as those ROM site stay alive you can play games on the DS. The 3DS can also run custom firmware to run roms so you might want to get a 3DS instead of a DS. Installing the custom firmware is really easy https://3ds.hacks.guide/