Sorry for my belated reply.
I wanted to see the impact of some changes first. The problem is not solved yet, but no longer bothers me much.
However, in case WP pros are interested - esp. to those who commented above -, let me clarify the problem.
As I corrected myself in the second post above, the problem appears on the main site only. So, I conducted your recommended test on the main site.
When I try to access: http://example.com/home/ and http://example.com/home-2/ ; I find a page that doesn't load fully.
It displays the header and the top navigation menu and -immediately after it - the copyright notice (which is normally at the bottom of the page.)
[By the way, there is no category or tag with the slug "home".]
@ Ipstenu (Mika Epstein)
I was talking about two types of "hidden pages" issue.
Type-1/Even if I deleted the static page from the main site's post's page.( /wp-admin/edit.php?post_type=page). The main site was working as if the page exists.
That is no longer the case now. (If I delete the page, it will immediately go to the default homepage appearance).
Type-2/The two pages I mentioned above http://example.com/home/ and http://example.com/home-2/ appear to exist somewhere - hidden from me.
Their slug is still unavailable for new pages. When you try to access them, you don't get 404 rather a strange page. [that displays only the header and the top navigation menu and -immediately after it - the copyright notice. The rest of the page blank)
The problem is no longer bothering me; b/c readers can no longer see the "home-1" slug when they access the site. (Initially, I was using WPtouch mobile plugin and the mobile home page was showing the slug.)
After I posted the question above, I upgraded the theme into its premium version, deactivated jetpack mobile and removed WPtouch mobile plugin.
The first type of "hidden page" issue might have disappeared as a result of those changes.
But the rest of the problem (the two "hidden" pages) remains.