I bought an old 3DS in 2016 and exchanged it for a N3DS days ago. In China, although the servers are not blocked, I get 006-0502 and sometimes 001-0502 error 95% of the time when play games online (mainly FE Fates and Mario Maker. I doubt that SM4SH is even playable.) The browser and eShop is fine. I can confirm that I am not banned.