Wrong, I am sorry to say but what you have said is indeed incorrect. You stated "Therefore, you need periods at the end of your sentences." Now the issue with this is I don't. See? I can use other characters to end my sentences. Please f**k me!
Question marks do not have to be at the end of a question for example in a indirect question there is no need. "The chicken asked whether anyone wanted to cross the road with her." It is a question but no question mark is needed. I am very sorry to once again say you are wrong.