These:
hussainsheikh PHP Warning: PHP Startup: Unable to load dynamic library 'php_mysql.dll'
PHP Warning: PHP Startup: Unable to load dynamic library 'php_interbase.dll'
PHP Warning: PHP Startup: Unable to load dynamic library 'php_oci8_12c.dll'
PHP Warning: PHP Startup: Invalid library (appears to be a Zend Extension, try loading using zend_extension=php_opcache.dll from php.ini) in Unknown on line 0
PHP Warning: PHP Startup: Unable to load dynamic library 'php_pdo_firebird.dll'
PHP Warning: PHP Startup: Unable to load dynamic library 'php_pdo_oci.dll'
are saying that your php.ini said to load these extensions. And it cannot load them. (some reasons why it cannot load them are: they do not exist, are the wrong version, or there is a problem with them). They do not appear to be anything that would interfere with osTicket running though.
I have no idea why you have a hard time with running this.
You set the email up in osticket (add account info) and enable it.
You go to Admin panel -> EMails -> Settings and enable Email Fetching, and disable auto-cron and set the default MTA.
Then you setup the Task scheduler to run the cron.php on a schedule.
Since you aren't getting any PHP errors or fetching any emails ... the only thing I can think of is that your environment has an issue.
Please go to:
https://docs.microsoft.com/en-us/iis/application-frameworks/scenario-build-a-php-website-on-iis/configuring-step-1-install-iis-and-php#13-download-and-install-php-manually
Start at step 5 and manually follow the steps up to step 18 to make sure that something isn't missing or done incorrectly.
Open a command prompt.
type cd c:\Program Files\PHP\v7.2.12\
hit enter
type php.exe -f c:\inetpub\website\support\api\cron.php
hit enter
What happens?