Is it mandatory to clear cache for each and every change made? It takes more time to clear caches and it also needs to be done more frequently for the each CSS or functionality wise changes.

Are there any alternatives available?
Disable Drupal 8 caching during development


  When you are developing a module or a theme you have to clear Drupal's
  cache (render cache, dynamic page cache, Twig cache) very often to see
  the changes being applied. You can disable caching for development.


Steps


Copy and rename the file sites/example.settings.local.php to sites/default/settings.local.php:



$ cp sites/example.settings.local.php sites/default/settings.local.php
 


Uncomment these lines in sites/default/settings.php:



if (file_exists(__DIR__ . '/settings.local.php')) {
    include __DIR__ . '/settings.local.php';
}



If you want to keep CSS and JS aggregation and preprocessing, change these lines in sites/default/settings.local.php to TRUE:



$config['system.performance']['css']['preprocess'] = TRUE;
$config['system.performance']['js']['preprocess'] = TRUE;



Uncomment these line in sites/default/settings.local.php:



$settings['cache']['bins']['render'] = 'cache.backend.null';
$settings['cache']['bins']['dynamic_page_cache'] = cache.backend.null';



Add the following lines to sites/development.services.yml:



parameters:
  twig.config:
    debug: true
    auto_reload: true
    cache: false




(source: drupal.org)