So many people lately have been reporting bans from playing sun and moon early, myself included. This tutorial will help get the 3ds working on the eshop and online games. I cannot confirm account based things like pokemon bank still work, but i would assume they do. Note that your friends list and games will still be there. Also note: you cannot access nnid settings after being banned, even after this method. You're eshop history will also disappear.
With that being said, here is what you will need:
1. the banned 3ds
2. An unbanned 3ds
3. Decrypt9 running on both.
Now here are the instructions:
1. boot up decrypt9 on the unbanned 3ds.
2. Go to sysnand options and dump you friendcodeseed_B
3. Put the sd card in the computer and backup the file you just dumped.
4. Not sure if i can share this, so i'll just mention where to get it. Theres a youtube video called [3ds] how to unban 002-0102. In the description theres a download for nnidsave.bin. Download that.
5. Now on the banned 3ds, go into decrypt9 and dump secureinfo_A
6. Open secureinfo_A in a hex editor. The very last line should be your 3ds console id. To confirm this, it should match up to the code on the back of your 3ds. Without changing the first 2 letteres, just change some random numbers and make a new id.
7. After that, put all 3 files you made/ downloaded in the files9 folder of the banned 3ds.
8. Go into decrypt9 on the banned 3ds and inject all 3 files. Congratulations your 3ds is unbanned.
As far as i've tested, the unbanned 3ds should still be able to go online along with the banned 3ds, but this is not certain. Also, just in case, do not share the friendcodeseed_B with anyone else, as i dont know what happens when too many 3ds's have the same friendcodeseed. Also if the 3ds blackscreens, that means your cfw is not compatible with the injection, but most are. If a mod could sticky this i think that would be a great help.