Is it going to be a problem if I promote my reference code on adwords? I'm also considering to promote my reference code on Facebook by paying money to Facebook. Is there any restriction about this issue?

Any time u r not sure about advertising, submit a support ticket to admin.

If you get an answer please do share with us, in my opinion I think ads for such sites can be frowned upon, I remember FACEBOOK blacklisted neobux and other PTC sites because they were heavily advertised. Any type of unsolicited spam is frowned upon and should be avoided. Ideally, you should advertise only on places that allow it or provide such a market place, and allow for such sites. Even though CS is no longer a PTC, these type of ads might be frowned upon. As far as google and/or facebook you should read their respective terms of service and guidelines, and of course check with CS as well - if CS allows it but Google and/or FB doesn't then you cannot