1. Sure. Any wheel stud, bolt, and or nut is permitted. And Wheel spacers are permitted.
2. I think you can modify but not remove.
3. MacPherson strut equipped cars may substitute struts, and /or may use alternate inserts.
Yes if the modification is part of the strut and no other piece that is restricted.
4. I cannot think of any justification for what I think you are suggesting
5. Oil cooler(s) may be added or substituted. Location within the bodywork is unrestricted, provided that it/they are not mounted within the driver/passenger compartment.

Sure but I do not see where you could make a body modification to duct air to the new location.