Can you use an sb nikon 800 flash with a nikon 610?

Can you use an sb nikon 800 flash with a nikon 610? - 1

Sure, have you not looked in the user manual for compatible flash units for your Nikon D610

Hint, look on pages 294 - 295 of your user manual

Yes but if it's not TTL compatible, you'll have to use the flash in Auto or Manual mode with the camera in Manual mode at a shutter speed that's equal or slower than the maximum flash sync speed.

Yes you can use it

Yes.