I usually moisten the base of the figure before positioning it on the fondant cake. I have also used small wooden dowels or tooth picks to secure larger figures.
No it cannot be put in freezer, just refrigerated. The moisture gets trapped and ruins it. I learnt that the hard way!
The 3 sizes of tourne potatoes are large, medium, and small. They refer to the dimensions of the potato after it has been cut into an oblong, barrel-shaped piece with seven equal sides. The size classification is based on the diameter of the potato before it is turned.