Is it possible to forward calls to a non Ring Central number after a certain number of rings?

Yes, this could be done.

It is pretty simple. This can be done for calls to your direct number or from the call cue and ring groups. I am not sure if a non-admin can do this because I am a super admin and can always do anything I need to, but if you can get to your User and call Handling & Forwarding section - assuming you have proper permissions, you can set it up yourself in a minute.