What happens if you click restart?

I'm just at flowey boss and I'm curious of what happens if you click restart Does flowey just cancel that or do you get to really reset? I don't want to try it cause if it restarts I'm gonna have to go all that through again..

I'm just at flowey boss and I'm curious of what happens if you click restart Does flowey just cancel that or do you get to really reset? I don't want to try it cause if it restarts I'm gonna have to go all that through again..