AutoCAD Inventor :: Draw 2 Hemisphere Structures Which Have Hall And Pillar?

Now I am trying to draw 2 hemisphere structures which have a hall and a pillar (bumo) like in the appended file.

Even though I used 2 rectangular parallelepiped in that, I like to use hemisphere.

1) How can I divide a sphere into two parts? 

2) How can I make them aprat to make a hall and  a pillar? I like to know how I can control them separately after separation.

3) Is there other way except 1) and 2) to make my model?

4) Is there a way to make one hemisphere? I think that I can use "draw sphere -> make workplane at the center of the sphere -> extrude cut half of the sphere".