First, is it possible to prevent some users from viewing some perspectives?
My goal is to prepair a "simple" perspective for non-experienced users and I would like to hide their "Default Perspective" button. I would like the default perspective to be visible only for more privileged users. Ideally, non-experienced users should not be able to customize their perspective at all.

And the second question: Is it possible (in some perspectives) to hide items in a context menu of objects in an Objects Browser?
A motivation is the same as in previous case: non-experienced users could be confused.