That's a big set of questions all at once.
First of all, there's no such thing as a spherical building, even if Archicad has a sphere object in the library folder "Special Construction." Or, that you could make a Complex Profile half-sphere and use it with a curved wall to define a sphere that would possess more built information than a fantasy sphere might. [see illustration attached]
A building that is spherical would be made of many flat segments - like a geodesic dome appears to be a sphere but is sticks and tilted flat panels. No curves there at all!
I remember a GDL object somewhere that was a Geodesic dome - perhaps one of the objects with the GDL Cookbook.
If this is a multi-storey structure, you could use the complex profile/curved wall approach to guide and define floor areas [floor plan cut height] and then replace it with arrays of tilted columns and triangular roof planes as interstitials.
Archicad doesn't map textures to curved or angular surfaces well, so trying to emulate the 3D with a surface won't do the trick for you.
Dwight Atkinson