Re: Enabling read-only access to the site
Sure it's possible. Please see doc.tikiwiki.org/Permission
and doc.tikiwiki.org/Group. The group you'd be setting permissions for would be Anonymous, which exists by default, so just assign the permissions as you please. Then if there are any pages, etc. you don't want anonymous visitors to see, assign the "view" permission for these pages in particular to, say, Registered. That means Anonymous can't see them. Similar pattern works for editing, admin tasks, etc.
-- Gary