Sharing Restriction - by default all users can see the CG-Button. If however you prefer that only managed-app admin will see CG-Button you can set this here. This will allow website admin to hare widgets with users but will not allow users to share widgets with each other.
Alias domains - when using custom-made apps and also for the purpose of giving special permissions to managed-app user account we check the current login user against domain name. If web admin run a website with alias domains you can add these aliases in this field so that we can recognize the admin login also when operating with the alias domain.
Special Layers - the special layers preferences let you define the preferred layer for specific pages. The layer determine the sharing context state or in other words with corresponding to web it define if a widget will be viewd only in specific page, on domain or on top-level domain and also if it wil be shared as private, closed for peers-group or that it will be public so that any user can see it. These settings are used for example when you want to set some page of your website as sharing board, so that all users can share with the public. In that case you will set the URL of this specific page, and define a public layer for a page.
* Note: when you work with this property the URLs you specify refer to pages on which all users will be able to share widgets with all the other users!