I'm not sure if I understand the problem... This is how you should create a public section and a member section.
1. Create a member groups and some members in the Site Settings.
2. Create a public section (let's call it Section A), and a member section (let's call it Section B) in your pages index.
3. Set Section B to be visible for members, through the page settings
4. That's it. If you're not logged in you see Section A, if you're logged in you see both section A and Section B.
If you want to have section B to look differently, just use another template for those pages. It just should look like:
- Home
- Section A
- Section B
So you probably need 3 templates: 1 for the homepage and 1 for each main section. Use the same menu call in each template. So don't use multiple menus. But if you want to hide the menu for Section A, when logged in, then use the code below to show or hide it according to logged in status. Or just use 2 separate menus.
Now, the login link. Have a look at the login droplet:
http://www.websitebakers.com/pages/droplets/official-library/other/login-form.phpPut that in a separate page and a login/logout form will appear. Just link to that page from the top right with the code:
<?php
if(FRONTEND_LOGIN AND $admin->is_authenticated()) {
echo "<a href=\"";
echo LOGOUT_URL;
echo "\">Log out »</a>";
}
else echo "<a href=\"your_link_to_the_login_page\">Log in »</a>";
?>
It will show a login link if not logged in, and a log out link if logged in. Or use it to link back to the public section like you wrote (not user friendly in my opinion).