Yes.
Canon EOS film cameras uses EF-mount lenses. All Canon EOS Digital cameras will also accept EF-mount lenses.
yes
Absolutely yes. Canon EOS 450D has the same mount as Canon EOS 400D, wich is EF and EF-S.
Yes, with a FD to EOS adapter.
Some popular Canon film cameras are the Canon EOS Rebel 2000 with 28-80mm lens, Cannon EOS ELAN 7E with 20-90mm lens, and the Canon EOS Rebel G Film SLR Camera kit with 35-80mm lens. You can buy these on any website.
EOS EF-S and EF... The Canon Rebel EOS is compatible with over 60 Canon EF/EF-S lenses A super high-end lens good for this camera would be one of the canon 70 200 lens. You can see a review of it at: http://canonlensreviews.net/canon-ef-70-200mm-2-8l-is-ii-lens-review/
Yes, the Canon EOS 400D has both EF and EF-S lens mounts. Therefore, the TS-E 90mm WILL fit on the camera because it has an EF lens mount.
Yes, you can. Any EF and EF-S lens will work on 20D.
EOS is Electro-Optical System. It controls the optics of a lens through electronic system.
That depends on the lens you put on the camera.
Yes, if you purchase the 'EOS' version of this lens (the one intended for Canon) it will fit just like any other 'EOS' lens would. I have the 500D and it fits fine, but a Google search will show others successfully using the Samyang 8mm fisheye with other Canons e.g. 450D.
Canon EF-S 17-55 f2.8 is a nice normal zoom lens.
yes all Canon cameras are compatible via lenses to each other