Question 4
Why is only about two thirds of the water added before the solid is dissolved?
The right answer is the one marked above.
So the solid can be dissolved before the volume is made up to the mark. Filling to the mark first means any stirring needed to dissolve the solid pushes the level past it, and once you are over the line the whole preparation has to start again.
The order of operations here is not arbitrary. Every step of the method exists to protect the accuracy of the final concentration.