#2: you can create material selections in cinema 4d.
There are several possibilities how this can be achived.
e.g. you can assign a material to a polygon selection directly by dragging it onto the selected faces (polygon mode)
or you can create a polygon selection manually (from the top menu, selection>freeze selection), give it a name and enter that name in the Material Tag under Selection
or in case you have several objects which have their own material (e.g. during construction of the model), combining them into one Object (select them in Object Manager,
right click and select Merge Objects from the context menu) will automatically create material selections.
Make sure that you don’t have any faces in your mesh with no Material assigned or faces that are assigned to more then one material, this will cause an error on import to UE4.
#1: hard to tell without seeing examples.
Some might use 360° Images on a Sphere, maybe even in combination with 3d elements like trees, cars, people etc.