1. You don’t need to register any items with included the theme. You’ll get updated versions over by the theme. Premium plugins will be alert to you when new updates available. You should delete old version of the update needed plugin and install it again over the Plugin installer under the appearance menu.
You ca follow the cosmos documentation at: https://themeofwp.com/theme/cosmos/doc/#themeoptions
Also you can use automatic demo installer or xml files for the demo like contents. Widgets, contents, images etc will be imported into your website.
Also you can watch our youtube help videos at: https://www.youtube.com/channel/UC72S-DG1fE6ZcEqOHulC_lQ/playlists
Please see the theme navigation settings above.
2. Yes the breadcrumbs will appears only with subheader.