I think it's safe to assume the flashcarts are not locked to any region, but do the roms have to be from a specific region, or can the roms be used from any region?
Sky3DS can play some games that are region locked if they work with Smealum's regionthree exploit.sky3DS is region locked, you need ROMs from the region your 3DS is in. Gateway isn't region locked, you can install whatever you want.
Sky3DS can play some games that are region locked if they work with Smealum's regionthree exploit.