So, do I have to cover with patterns the whole town? Would it be sufficient to strategically place one in a 9x9 square, so to not leave enough space for a new villager to move?
technically you don't have to cover the whole town with paths. if you want your villager to move into ONE specific are of town, you just have to ensure that all of the other possible 3x3 plots that would allow for that villager to move in are covered. what i like to do is pick a corner of town and start placing paths in a dot grid pattern with two spaces in between a path. this is what i mean:
P - x - x - P - x - x - P
x - x - x - x - x - x - x
x - x - x - x - x - x - x
P - x - x - P - x - x - P
x - x - x - x - x - x - x
x - x - x - x - x - x - x
P - x - x - P - x - x - P
P are squares with path placements, x are empty squares. this ensures that there isn't a 3x3 space available for any villagers to put their house in in that whole grid. it sucks and is kind of tedious, but it gets the job done. if a rock, tree, flower, buried object, or something else that prevents placement of paths is in the way of the path grid, i just make a star pattern with paths to ensure that there isn't a 3x3 space left anywhere because an object is blocking where i would put the path. so like this:
P - x - x - P - x - x - P
x - x - x - x - x - x - x
x - x - x - P - x - x - x
P - x - P - T - P - x - P
x - x - x - P - x - x - x
x - x - x - x - x - x - x
P - x - x - P - x - x - P
since the object (in this case a tree as indicated by T) blocks where i'd put the path (and would allow for a 3x3 area to exist if nothing else was placed there to prevent a plot), i just put paths at the four cardinal directions from the object. you can do this with your whole village and ensure there aren't any spots where a villager can move but the one you want.
If I prefer another villager than the one that moved in, would plot resetting change the villager too?
depends. from what i've read, potential move-ins that happen naturally are determined by a couple of different things that take priority over each other. this seems to be the priority:
- was this villager moved in by amiibo card?
- was this villager asked to move in via another town or through the campsite?
- was this villager floating in another town's void that you visited?
- was this villager determined to move in by the game based on your lack of personality types?
for all of the options except the last, the villager is usually a specific one. for the last option, when the game chooses a character to move in based on your lack of personality types, it seems to pull from a pool of different characters that meet the game's requirements. this is how you can plot reset for different villagers of the same personality type. realize that there is a finite number of villagers the game chooses for you, though, and it seems to be somewhere in the 5-10 range.
Do I have to save a little bit before six a.m or anytime the day Before the villager moves is ok?
the only difference between saving and quitting at 5:59am the day the villager should move in and 6:01am the day before is that you don't have to wait as long in realtime before you can start plot resetting with the former choice. if you save and quit at 5:59am the day the villager moves in, you only have to wait for 1 minute before starting a new save and beginning your plot resetting adventure. if you save and quit any earlier, that means more time you have to wait to have passed with your town not loaded. i usually recommend TTing to 5:55am the day the villager is moving in, then saving and quitting as soon as the game is loaded, that way you don't accidentally TT to 5:59am and get distracted and take too much time and end up saving and quitting at 6am or later, which progresses your village to the next day and prevents you from plot resetting.
If I discover the new plot with my mayor, is it too late and I can't reset to another position?
yes. any resident of your village that discovers the plot causes the game to save the plot position, even if you close without saving. this is why you make a new character to check the plot, because the game doesn't save the plot location on a character that doesn't exist as a resident in your village yet.