I'm not sure what you mean by "officially done" with the questions. You have to be registered with the clearinghouse, which means answered their questions and paid your fee. Once that is done, you may take official visits.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .