will all ef lens work on 6d?
But, just the "EF" lenses. Any Canon "EF-S" lenses will not work. Any third party lens made for Canon full frame lenses will work. But, any third party lenses made for "Canon APS-C" bodies will not work, because they would be equivalent to an EF-S lens.
"... any third party lenses made for "Canon APS-C" bodies will not work,..."
This is only partly true. Some, maybe all, third party lenses will mount to an 'ef' body. They can even 'work'. Poorly but they will work.
Canon ef-s lenses will not even mount.
An internal focus lens (sometimes known as IF) is a photographic lens design in which focus is shifted by moving the inner lens group or groups only, without any rotation or shifting of the front lens element. This makes it easy to use, for example, a screwed-in polarizing filter or a petal shaped lens hood upsers.