Question 1: In order to sculpt a specific area, I turned on the automatic grid. However, when I used the move-brush and tried to smooth it afterwards, it became ineffective and caused the grid to become larger. But when I used the add-brush, drew something freely and then smoothed it again, it became effective once more.
Question 2: I’m not sure what brush I clicked on, but suddenly all of them disappeared. They only reappeared when I went back to the previous step.