44 magnum and 44 special.
250 USD
50-160 or so
Yes. The 44 special is a bit shorter than the 44 magnum, so it will fit in the cylinder of the 44 mag. The reverse won't work, however. A 44 mag cannot be fired in a revolver chambered for the 44 special because the 44 mag is too long and won't fit in the cylinder of the 44 special.
Single Action revolver made in Germany.
No! They will not even fit in the chamber.
50-260
No. While Dan Wesson DID make a .44 Magnum revolver, it was not known as a Desert Eagle. IMI made a .44 magnum Desert Eagle Auto pistol, but not a revolver.
50-500 USD depending on specifics
As long as both the rifle and the revolver are chambered in .44 magnum you can use the same ammunition for both. I have a Henry rifle in .44 mag and a Ruger redhawk .44 mag and I use the same ammo for both. That's one of the nice things about that caliber.
There is no such weapon.
300-360 USD