Reset button in form can be added directly in buildForm method of Form class or using a form alter.

$form['action']['reset'] = [

     '#type' => 'button',
      '#value' => 'Clear',
      '#attributes' => ['onclick' => 'this.form.reset(); return true;'],

];

You can use the following block code to load a form in a block in Drupal 8.

<?php

namespace Drupal\example_module\Plugin\Block;

use Drupal\Core\Block\BlockBase;

/**
 * Provides a 'ExmpleFormBlock' block.
 *
 * @Block(
 *  id = "ExampleFormBlock",
 *  admin_label = @Translation("Example Form Block"),
 * )
 */
class ExampleFormBlock extends BlockBase {

  /**
   * {@inheritdoc}
   */
  public function build() {
    return \Drupal::formBuilder()->getForm('Drupal\example_module\Form\ExampleForm');
  }

}
 

Example Form is the class of form which has to be displayed in the block. You can also use core and contributed provided forms.

Since comment post is a form, the submit button text can be changed via form alter the in following way.

/**
 * Implements hook_form_alter().
 */
function your_module_form_alter(&$form,  FormStateInterface $form_state, $form_id){
if($form_id == 'comment_comment_form') {
  $form['actions']['submit']['#value'] = t('POST A COMMENT');
  }
}

Views output can be fetched in the following way : 

use Drupal\views\Views;

$view = Views::getView('YOUR_VIEW_MACHINE_NAME');

$view->setArguments($args); //Set Arguments if any.

$view->setDisplay('YOUR_VIEW_DISPLAY');

$view->preExecute();

$view->execute();

$content = $view->render();

Since taxonomy term is an entity all the Terms for a specific vocabulary can be fetched using following entity query.

$query = \Drupal::entityQuery('taxonomy_term')->condition('vid', 'YOUR_VOCABULARY');
$result = $query->execute();
foreach ($result as $key => $value) {
      $result[$key] = Term::load($value)->getName();
}

$result can used for getting key value array of TID and Term Name.

JS library to a view can be attached using hook_views_pre_render(). Use the following code to achieve it:

/**
 * Implements hook_views_pre_render().
 */
function your_module_views_pre_render(ViewExecutable $view) {
  if ($view->id() == 'YOUR_VIEW_ID' && $view->current_display == 'YOUR_VIEW_DISPLAY') {
    $view->element['#attached']['library'][] = 'your_module/your_library';
  }
}

You can provide an internal link from links.menu.yml in following way:

your_module.your_link:
  title: 'Menu Link Title'
  url: 'internal:/admin/an-internal'
  description: 'Menu Link Description'
  parent: system.admin_content
  weight: 120
 

You can use the following command to turn off the apache 

sudo launchctl unload -w /System/Library/LaunchDaemons/org.apache.httpd.plist

You can use hook_views_pre_render and change the value of the field in the following way. In this, I have removed field_image from 2nd row in the view. 

function your_module_views_pre_render(ViewExecutable $view) {
  if ($view->id() == "view_id") {
      foreach ($view->result as $key => $value) {
        if($key == 1 ) {
            $value->_entity->set('field_image', ['target_id' => 0]);
        }
      }
  }
}

jQuery file can be added to the controller in the following way:

In the controller, file make sure that library defined in libraries.yml is returned along with the markup,

return [
      '#type' => 'markup',
      '#markup' => '<div id="my_js_application"></div>',
      '#attached' => ['library' => ['example_module/example_library']]
    ];

In the libraries.yml, the example_library has to be defined.

example_library:
  version: 1.x
  js:
    js/myapp.js: {}

dependencies:
    - core/jquery

Now in myapp.js use the following syntax :

(function ($, Drupal) {

}(jQuery, Drupal));