Ok paul on the RH hanger very simple way is to just delete the last operation in feature manager tree.
So delete Body-Delete operation or drag the blue bar up above it which will take you back one step.

Then if you want make a mirror with some separation between the parts create a Plane parallel to the edge your mirroring from and set a offset distance. Then use mirror function and select bodies to mirror option and click on part then uncheck Merge solids.