The axis of rotation need not go through the body.
In all of them, the first and third rotation axis are the same.
"I remember no relationship between the axis of rotation and our direction."
Therefore an axis of rotation cannot be used in four dimensions.
The axis of rotation does not have to be inside the enclosed area.
This connection in position is important due to the process of the Earth's rotation axis.
Take A - the dot in the middle is the axis of rotation.
Now, if she pulls just one arm in, she'll change her rotation axis.
Only the points on the axis of rotation will be unaffected.
However, over thousands of years their direction averages to the Earth's rotation axis.