No I'm sorry but I don't believe so... It is either activated for everyone (though whether or not they wish to display it is up to them in their settings) or deactivated all together.
I'm sorry you kind of lost me there... Do you just want to post the code because you could always just post the code in a board with restrictions. I thought you talking about setting HTML to only work for some people when used in posts... for it to be used in posts with a working result it would have to either be for everyone or no one... if you are just looking to put the code thought in a restricted board and not actually show the result of the html... that could be done.
there is no one way to restrict a html page. there is some codes you can use to put a pass protect on it. but they are really not secure and anyone with a little know how could get right in.
your best bet would be to create a forum for only staff/mods or what group you want to allow access to. then post it in a post there. just be sure to set your forums permissions for that forum to only allow whatever groups you want.