Someone can answer better I’m sure, but here’s my take:
1) there is a dropdown with the material you have created. here you can rename/alter and use to assign to any object. I haven’t figured out if you can select multiple objects and assign the same material.

2) not sure what you mean here. my guess is the world tab where you can assign a global color to the view

3) once you move a newly created object the controls to add/lower segments goes away. you have to add these options before moving or transforming the object.
Hope these are accurate and help. Like your image above.