My other 3DS wasn't updated to the latest firmware when I initially loaded up the physical cart, after I did so, it wouldn't let me start the game up either until I updated via eShop.
I've put my Welcome Amiibo updated Catridge into another 3DS, and the game will load, but your save file is completely gone until you update that 3DS to the latest Animal Crossing update. It will act as if it's a new game.
I also have a digital copy as well as retail and yes, you can play both...
I'm in need of the following sets!
I'll give you the freedom of naming your price, but if I recognize something as ridiculously overpriced I reserve the right not to buy it.
I don't have a ton of TBT to work with, so sadly I won't be able to get everything with TBT and will have to stop at some...