A little confused by your question, so I'll just say something about Sigma autofocus lenses and Nikon bodies. If you're wondering if the lens will focus the answer is yes, it will. If you're talking about manual focusing a Sigma lens on a Nikon body the answer is you only have to throw the switch on the body if the lens doesn't have its own focus motor. For example, with my 150-600mm, 105mm macro, 24-35mm, and 8-16mm, simply throwing the switch on the lens is enough. With my 15mm fisheye I need to throw the switch on the body from AF to M in order to turn the focus ring as it utilizes the focus motor in the body.
If you weren't wondering either of these things then remember it anyway, because one day you might.