There are several ways to check the version of the MySQL service on your account.
The first one is via a PHP script. You have to create a new file on your account, for example mysql.php, and inside it place the following:
Again replace USERNAME with your cPanel username and PASSWORD with your cPanel password. Then open the file in your browser and you will see the MySQL version running on the current server.
You can create the file via SSH, FTP or from your cPanel -> File Manager tool.