This is my attempt to explain the 3DS hacking ELI5. Currently all 2/3DS models can be hacked. You can put homebrew or CFW on it.
What's O3DS?
Old/Original 3DS. It includes the original small 3DS, the later released, bigger 3DS XL/LL, and 2DS.
What's N3DS?
New Nintendo 3DS. It's the newer...