I'm doing a paper on the capitol is there any rooms you can't visit there

I know you can't go up the last set of stairs to go into the gallery balcony, and there are some roped off rooms you can only peer into. I would recommend a visit.

Most of the building is open to the public. They offer guided tours so take advantage and ask questions.

Yes and beautiful ! Many rooms real interesting stuff

Yes.. somewhere I once found the blueprints online.. they have offices and such.. but you'll still be able to see the most important areas.. history wise.