How do you the bit " Draw a diagram to suggets a 3d shape for the ring"
For cyclic six membered rings there is a convention that involves drawing the molecule in either a "chair" or a "boat" conformation. These conformers allow the carbon (or nitrogen) atoms to adopt tetrahedral geometry and the chole structure is strain free.
Chair and boat mean nothing without a diagram. The chair conformer is the most stable for steric reasons.
I guess that the 3D (non-planar) shape has something to do with the bonds on the nitrogens. They must have an angle that non-planar structure can't exist.
It's a horrible question tbh
Just wondering do you have access to the May/June 17 papers like F331-F335?