Access Rules for the Administrator
I had mistakenly done two sets of access restriction rules.
The first one was correct, which was the <?php echo $_SESSION['UserLevel']; ?> = 3 (im my case for the administrator, the users rights were working fine, so I was able to login and log out and not see the pages after hitting the back button on the browser.
The second one, which should not exist, and after a few comparisons, trial and errors, I found out that it was:
<?php echo((isset($_POST[""]))?$_POST[""]:"") ?> = <?php echo((isset($_POST[""]))?$_POST[""]:"") ?>
So this restriction RULE should not be there and then I deleted and it worked fine.
So you were right, my problem was somewhere else, it was here in the access restriction rules. But you also mentioned something here
that was not mentioned before or I was not paying attention to it. That this restriction access code should be inside also on the LOG OUT page.
But you know, mistakes like these make us search deeper into the problem and in return we end up learning more.
Thank you for your help in helping me understand the problem.