I have a few copies of the game floating around my house and I found making money off turnips is really easy with two towns. Use your second copy to time travel to find a high selling price then invite yourself over and sell your turnips. Then again that will only work if you have to consoles...
I'm pretty sure you need the welcome amiibo update installed on all consoles you wish to play that game. Same thing happened to me just update the system and the game you should be good.
ah this is tricky because they will move to the same spot but with a lot of plot reseting you can get them to move. (This has been my personal experience anyway)
I once recieved a bannanna the villager then said "wow since i've finished using this i figured you could have it!" Lets just say i was pretty amused/uncomfortable about that situation ahhaha
Amiibo Figures - These can be scanned in to bring NPC's to the RV park, whoever you scan in will leave their position for the day to go on "holiday." EG. If you scan in Reese from Re-Tail Wisp will take over jer position and you can't sell anything that day, but you get Reese's rare furniture...
This has happened to my SD card and how i fixed it was to unscrew the back of my console and take out and clean the SD card. My SD card has been fine ever since then.
On my normal 3DS I have about 600 hours and in my new 3DS I have over 700, and i first started playing in September of 2015 and last played yesterday ahaha.