hello if your nikon camera is af mount, yes, you could make the sigma 70-200mm f/2.8 ex dg apo hsm large aperture macro zoom lens work with canon with this adoptor 

Yes. I have the same lens and adaptor on my Sony a7ll and it works beautifully. The m42 is also known as the 'universal' mount as other 3rd party camera and lenses also used it. I own 6 other K&F e-mount adaptors to different lens makers (ltm, MD, CF/CD, Nikon) and they all are well built with a nice snug fit. Highly recommended. 

The adapter is designed for Nikon lenses, including D mount. If the Tamron fits the Nikon D80 it should work. As for the lack of aperture ring on the Tamron ... not sure about that. Perhaps the Nikon D80 has an in camera aperture selection. 

I don’t think so. I night this to use on my Nikon D3100 with a Tamron 70-300. Neither are very heavy but this head would not keep my camera still. It crept down no matter how tight I made it. I think your camera and lens are heavier so I would go with a better name brand. 

I actually have not received this adapter yet. It's shipping from China. Don't think that was disclosed in the ad. However, I do not believe this is for the Pentax Q body rather for digital and film cameras that take the Pentax K mount in its many variations. So I'm expecting to be able to mount my Leica M mount lenses on my digital and film Pentax K mount cameras, no autofocus or relay of exposure information, only to be used with manual focus and exposure.