Inner Focusing Lens

Inner focusing on Canon lenses.

Does it mean visible size of the lens doesn't change (even at zoom lenses)?

Does the the lens extends, when zooming like at 35mm, it's the longest, shortest when it's at 16mm? (i.e ef 16-35/2.8L)

You asked:

Does it mean visible size of the lens doesn't change (even at zoom lenses)?

Answer: Yes.

Does the the lens extends, when zooming like at 35mm, it's the longest, shortest when it's at 16mm? (i.e ef 16-35/2.8L)

Answer: No, not the 16-35 2.8L or any other Canon inner focusing lens. The 28-70 2.8L is an example of a lens that extends when zoomed.

Scott