Can you change canon lenses on all canon dslr models?

I have 3 questions actually:

1. Can you change CANON lenses on all canon dslr models?
2. Can you change NIKON lenses on all NIKON dslr models?
3. Can you interchange NIKON and CANON lenses for both models?

I'm planning to buy a DSLR, I just want to know which one is flexible in case I buy both of these brands.

1) You can use an EF-S and EF lens on any Canon DSLR. You can't use EF-S lenses on APS-H and FF bodies. Older FD lenses will NOT mount on any Canon DSLR.

2) All AF, AF-I and AF-S lenses will work on all Nikon DSLRs. DX lenses will vignette on FF bodies, though.AF lenses will not autofocus with the D40, D40X, D60, D3000, D3100, D3200, D5000, and D5100.

3) There are adapters available for this, but don't bother. If you own a Canon DSLR, buy Canon lenses, if you shoot Nikon buy Nikon lenses.

Go to a local camera shop and try out the Nikon D3200 and the Rebel T3i and T4i.

Regardless of which camera you buy, you'll also need a genuine spare battery, 2 or 3 8GB Class 10 SD cards, a card reader and a case. A few basic photography books wouldn't be a bad investment.

1. All but the very old ones
2. All but the very old ones
3. There's an adapter for Nikon lenses to go on Canon cameras, but the auto controls won't work.

1) yes and no. Only EF lenses can be used on 5D and 1D series dSLR's. EF-S lenses will damage Canon full frame cameras All the APS-C cameras can use EF and EF-S lenses. NO FD/FL lenses can be used on EOS dSLR cameras

2) yes but for a couple of exceptions. Entry level Nikon dSLR cameras used AF-S lenses if you want to shoot in auto focus. All Nikon dSLR cameras that cost over $1, 000 can use any AF, AF-I and AF-S lenses as well as manual focus AI Nikkor lenses. Any Nikkor DX or FX lenses can be used on any of the Nikon dSLR cameras.

3) Nikon and Canon lenses are designed to use on only their respective brand cameras

Note: I use lenses that are over 30 years old on my F4, D300 and D3.

1. Of course.
2. Of course.
3.No.

Find one brand and stick with it - neither lenses or flashguns are interchangeable between brands. Just about any Nikon lens fits any Nikon camera, Canon EF lenses fit both film and digital SLRs, Canon EF-S lenses only fit their cropped-sensor DSLRs (e.g.a basic T3i accepts EF or EF-S lenses, the EOS 1D and -5D only take EF). Any Pentax lens made since 1975 will fit a Pentax DSLR, Sony take their own or Minolta AF lenses, and Olympus take 4/3 (not micro 4/3) mount lenses.

Third-party lenses have to be bought in a specific fit.

Sony, Olympus and Pentax all make cameras that do the same job - Sony's SLTs are better for video.

Canon and Nikon are not the entire camera market.

Nikon DX lens will not vignette on full frame bodies because when mounted the full frame bodies will automatically switch to DX mode.