Override Civicrm Utils file /sites/all/modules/civicrm/CRM/Utils/ReCAPTCHA.php to /custom_code/CRM/Utils/ReCAPTCHA.php . it is not working. I have cleared the drupal cache and also cleared /civicrm/admin/setting/updateConfigBackend?reset=1 cache. What thing is missing please guide me how can override civicrm files?
First of all, you should really customize CiviCRM by developing extensions. There is a developer guide that will explain you how this is done: https://docs.civicrm.org/dev/en/latest/
If you do want to override anyway, you should first of all navigate to Administer>System Settings>Directories to provide the path to the PHP files, have you done this? If you have it should work but I would still recommend to take the extensions route as this is by far the most used and supported route.