It could be that you've been blocked because of inappropriate behavior while on WikiAnswers (whether questions or answers).
It is perfectly safe to sign up for WikiAnswers.
No, you have do be at least 13 years old like it said when you try to sign up.
You just press sign out.
No, a Wikianswers account is free of charge.
You have to sign up for it.
Then you have to go to a different website or create an account and ask again (if you already have an account then sign in and ask again) and check back to see if it gets answered.
When you sign up for WikiAnswers, you are asked to choose your own username and password; you can personalize it from there during the sign-up process.(See the Related question on how to become a member of WikiAnswers.)
You can. You have to create a user name and password though, just like an email account. Then you can sign in!
Many people are here on Wiki Answers. If you would like to join, click sign up.
You don't have to login it is not mandatory.
You can't
No, You cannot log on to Facebook from WikiAnswers. You can sign into WikiAnswers using your Facebook account however.