live server shows 404 error, but not on local, codeigniter 3 - php

Question

I have four identical pages that only differs in some identifiers but the logic is very much the same. All of them works on localhost. Three of those pages works okay on live server, but one of them returns a 404 for some reasons I can't understand.
I use XAMPP 3.2.2 and Sublime for developing it on local. I moved it to GoDaddy Deluxe Linux for live. My Codeigniter version is 3.1.10.
I already tried answers from most of the questions on StackOverflow:
All controller and model names' first letters are capitalized in the file name and inside the file.
All of the .htaccess codes on here: https://github.com/tasmanwebsolutions/htaccess_for_codeigniter
I have two .htaccess files, one of them is inside the application folder, and one is outside. I don't know if that's confusing the system? But I have another website on a different hosting that has the same .htaccess files and they're working okay. And anyway, if that's confusing the system, why does it only affect one of the four identical pages?
.htaccess outside application folder
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /index.php/$1 [L]
</IfModule>
.htaccess inside application folder:
<IfModule authz_core_module>
Require all denied
</IfModule>
<IfModule !authz_core_module>
Deny from all
</IfModule>
All of the controllers of the four files has this up top:
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
//session_start(); //we need to call PHP's session object to access it through CI
class Question1 extends CI_Controller
{
and the rest is normal code stuff that are working on three of those four files.
In config. php I have:
$config['uri_protocol'] = 'REQUEST_URI';
and base_url is great.
Models and views are okay, as far as I can see, and the rest of the website is functioning alright with the included .htaccess. My routes are working okay, as well.
I'm so lost right now.
PS. I have a custom 404 page. When I input assessment.com/index.php/question1 it shows that custom 404 page. But when I open assessment.com/question1 it shows codeigniter's own 404 page (and not my custom one, for some reasons). I think that tells something, I just don't know what.
EDIT
Here's my routes.php:
$route['default_controller'] = 'home';
$route['404_override'] = 'Error404';
$route['translate_uri_dashes'] = TRUE;
I opted not to do
$route['question1'] = "Question1";
in routes because it doesn't change anything.

Answer 1

Check your APPLICATION ENVIRONMENT mode. You can find it on your project root_folder/index.php and at line no. 57.
define('ENVIRONMENT', 'production');
Change the ENVIRONMENT mode into the development mode, that is
define('ENVIRONMENT', 'development');
Then refresh your applications again. If you see CodeIgniter default error you can understand your CodeIgniter application are running ok and check out the error.If it doesn't show any error then your .httaccess has any error. I solved it my 404 error with this code, you can check this out.
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_URI} ^system.*
RewriteRule ^(.*)$ /index.php?/$1 [L]
RewriteCond %{REQUEST_URI} ^application.*
RewriteRule ^(.*)$ /index.php?/$1 [L]
RewriteCond %{REQUEST_URI} ^asset.*
RewriteRule ^(.*)$ /index.php?/$1 [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
</IfModule>

Answer 2

Answering this for the others who might come across the same problem.
Okay so user Don't Panic suggested I echo just "question x" in the problematic controller, and when I did that, the 404 error went away and it echoed the "question x." So definitely it's my controller that has the problem and not my routine or .htaccess files.
Now this controller is designed in such a way that it calls first an ID from the database before it shows anything. After I echoed "question x" I realized that the ID it is calling from my database has a value of zero. So, unsurprisingly, from the controller's point of view, the page doesn't exist! Hence the 404.
I've fixed it now by updating that table from my database and giving the ID a value it should already have had in the first place.