An issue with multiple routes with its own twig template of custom module

Question

First time I am creating a custom module in Drupal 8. I have some pages having only HTML markup and JS code.

Assume I have 3 pages flow and user goes to 1st page (next button) -> 2nd page (next button) -> 3rd page.

To achieve it I have created a custom module as below. My custom module requires multiple routes with its own separate twig/view template.

The name of my module is custom_demo and it is created at /web/modules/custom/custom_demo with necessary artefacts as below.

The issue is first 2 pages work, the moment I click on next button to go on 3rd page, it does not work and shows The requested page could not be found. message.

Working

http://mysite.dd:8083/mypage/page1

http://mysite.dd:8083/mypage/page2

Not Working

http://mysite.dd:8083/mypage/page3

custom_demo.info.yml

name: Demo
type: module
description: 'Demo Description'
package: Custom
core: 8.x

custom_demo.routing.yml

custom_demo.page1:
   path: '/mypage/page1'
   defaults:
      _controller: 
        '\Drupal\custom_demo\Controller\DemoController::page1'
     _title: 'test title1'
   requirements:
   _permission: 'access content'

custom_demo.page2:
   path: '/mypage/page2'
   defaults:
     _controller: '\Drupal\custom_demo\Controller\DemoController::page2'
     _title: 'test title2'
  requirements:
    _permission: 'access content'

custom_demo.page3:
  path: '/mypage/page3'
  defaults:
    _controller: '\Drupal\custom_demo\Controller\DemoController::page3'
    _title: 'test title3'
  requirements:
    _permission: 'access content'

custom_demo.module

<?php

function custom_demo_theme($existing, $type, $theme, $path) {
return array(
  'demo_page1' => array(
    'variables' => array('title' => NULL),
    'template' => 'demo-page1',
  ),
  'demo_page2' => array(
    'variables' => array('title' => NULL),
    'template' => 'demo-page2',
  ),
  'demo_page3' => array(
    'variables' => array('title' => NULL),
    'template' => 'demo-page3',
  ),
);
}

/src/Controller/DemoController.php

<?php

 namespace Drupal\custom_demo\Controller;

 use Drupal\Core\Controller\ControllerBase;


 class DemoController extends ControllerBase {

public function page1() {
    return array(
        '#theme' => 'demo_page1',
        '#title' => 'test title1',
    );
}

public function page2() {
    return array(
        '#theme' => 'demo_page2',
        '#title' => 'test title2',
    );
}

public function page3() {
    return array(
        '#theme' => 'demo_page3',
        '#title' => 'test title3',
    );
 }
}

Twig templates

Under custom module folder I created the folder /templates and created following 3 files with some test content.

1. demo-page1.html.twig
2. demo-page2.html.twig
3. demo-page3.html.twig

Can someone please help, why the http://mysite.dd:8083/mypage/page3 is not woking?

Thanks - Hitesh