if you have any turnips then they'll rot, but other than that there are no negative effects as far as I can remember. The game treats it like TTing one day forward so you don't really get weeds or anything
yes. the only consequences for time-travelling are weeds and the nook miles achievment is not accurate anymore
if you didn't travel more than one week forward, Isabelle will not make the announcement of a new day, the game will just start like nothing happened
I lost a house upgrade I paid for when I TTed back one time, and had to request it again. I know others have noted that upgrades don’t progress when you move the date back. So, imo, it’s best to be safe and complete any upgrades b4 TTing back.
I went back to my time! all is good?
I say good? because a villager was switching with an amibo villager and now the AV's house is there but she is no where to be found
it glitched? o: i think it's possible her house might have stayed but the new villager's moved in already. it happens sometimes when you TT back and forget to completely finish letting a new villager move in and replace someone/an amiibo villager (it's the case now for me, felicity replaced prince but i forgot to completely get her out of move-in boxes so her house exterior is prince's)
Other than turnips rotting, you should probably not TT backwards until a villager has moved out / moved in completely! I’ve had this happen where the exterior or interior of their house glitches!