Are they correct?

I have some accounts IN/ON social networking sites.
I often visit my facebook page/profile/account.
Do you have profiles on any social networks?
Have you already had an account IN/ON any social networks?
Can you agree that you are dependent on social networks?
Have you already registered your profile on any social networks?

Which/What social networks listed below do toy usually visit?

Can you suggest your own ways for writing the sentences?
Thank you!