Re: cutting from the inside part of an object?
Hmmm. Easiest way is probably to make a cylinder, cut away half. Make a divided cube--so you have points in the middle to join the cylinder center vertices to--and remove one face of the cube. Then merge them together. You can use Snap Vertices by Distance with a small distance to merge the points together so you don't have to snap them by hand.
That will give you something like this:
|