Nurb Solids


I’ve been trying to understand how exactly are solids constructed in rhino?
according to the nurbs we should have 3 knot vectors and their corresponding control points.
When building a solid on rhino it only builds multi-polisurfaces where i dont find a option to view the control points rather the only option is the meshing option.

How exactly are solids modeled?
is it possible to obtain the 3 knot vectors and the control points of a solid?
is it possible to refine the degree of the nurbs/splines and the control mesh as in a nurb surface (rebuild command)?
is it possible to extract it to a .txt file?

thanks in advance.