You mention that "We can't add Map Service that has been shared from ArcMap 10.1". Did you create hosted feature services that are on ArcGIS.com in an organization? First, make sure that your hosted feature service is editable within the properties on ArcGIS.com. Next, you can sign in to ArCGIS.com using your organization account in the Flex Builder application and then add your feature services. In the Edit widget, your feature service should be listed as editable. Any changes will be synced automatically to the hosted feature service, (you can make edits in the Flex application and then open up the feature service in the ArcGIS.com Map Viewer to see the changes).