Yes, the Tokina 100-300 AT-X AF lens is compatible with the Nikon D5000, as it is designed for Nikon F mount cameras. However, since the D5000 does not have a built-in autofocus motor, autofocus functionality may not work with this lens if it doesn't have its own motor. You can still use the lens in manual focus mode without any issues.
No as long as they have the correct mount.
Yes, it will fit. However, you will still need to see if the lens you have has or does not have features like autofocus or CPU connectors that will carry all the info that your camera needs... If it is a Nikon Lens it will work fine. So will others like Sigma, Tamron and Tokina. Carl Zeiss may not give you all the functions but will work in manual mode.
Yes
Yes
No, a Canon lens will not fit on a Nikon camera because they have different lens mounts.
yes, sure can
I think so
No, a Canon lens cannot fit a Nikon camera because they have different lens mounts.
yes
A Nikon EM has a standard Nikon mount, so you can use any lens that'll fit on a Nikon, except for a Nikon Series G lens, on an EM. A Series G will fit but it won't work because there's no aperture ring.
No, Canon lenses do not fit Nikon cameras. Canon lenses are designed for Canon cameras and use a different lens mount system than Nikon cameras.