For your earlier question about the tyre wall being mirrored, it could be the surface normal is pointing the other direction, try force 2 side on the material to see if it renders ok, if not, rotate the U or V angle to 180 degrees of the bitmap in your material editor.
Q1, You can adjust the pivot of any object. Go to the Hierarchy tab, then choose Pivot, select 'Affect Pivot Only' then you can move your pivot points about. Once finished, remember to de-select 'Affect Pivot Only' button.
Q2, You can do that, some people prefer this way, but you will have to flip the surface normal to point inward, or force 2 side material. because if you don't do that, the inside of the sphere will not render.
The other way is go to Enviroment and assign an enviroment map to the Background. Make sure your mapping is checked on 'Environ' and 'Spherical' and on your Sky light, check on 'Use Scene Environment' that will use the bitmap colour for your light.
Q3, for the scene you have at the moment, it is like a sunset, I don't think you will need a spot light as the sun has gone down, there is more ambient light around and the shadow should be more difussed. The light needs to be slightly warmer and you may need an environment reflection map for the reflection to reflect your background image.
Q4, I don't have a UFR, I can't answer you on this one, but you can always create your own texture by taking a few photos of your own.