How do I hide specific node fields to users not registerd to that specific node?
You need  to use Field Permissions module, with the help of this module you can do your stuff. Which allows site administrators to set field-level permissions to edit, view and create fields on any entity. With this module you can hide the certain node field to anonymous user.




  
  Enable field permissions on any entity, not just nodes.
  Role-based field permissions allowing different viewing patterned based on what access the user has.
  Author-level permissions allow viewing and editing of fields based on who the entity owner is.
  Permissions for each field are not enabled by default. Instead, administrators can enable these permissions explicitly for the fields
  where this feature is needed.