So in Joomla you may choose what kind of menu item you make, e.g. to an article or a 'system link' like this. On a multilingual site, I have in the mainmenu a button that links to an alias. The problem is, that the default template, Purity III, is assigned to this menulink, whatever I try to do. So I end up having the menu of one of the languages (that of the default assigned Purity template) on the page of whatever menu-alias I make.
In the Purity III template, you have to assign which menu you want to show, so with multi-language sites each language should have it's own template.
About the alias: The alias is an alias to a hidden menu-item. In order to show a loginpage when a user is not logged in this menu-item's access is limited to registered.