The first one in the active voice and the last one in the passive voice are grammatically correct. The second one is incorrect. 'Know' refers to a state while 'get' needs an action like 'get arrested'.
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 .