If one has access to yourdomain.com:2082, then one has access to phpMyAdmin. Again, phpMyAdmin is similar to other 3rd party applications that included with our product: we handle the security and auth exchange. To my knowledge, there cannot be a separate password for a phpMyAdmin. If one has a phpMyAdmin username that's the same as the domainowner username, they must be synchronized. phpMyAdmin must be set up with a created database username and password. Like any other php-based application, you cannot access the database from an the application with the master username and password. It must be set to use a separate database username and password.
Is possible to ask hosting to set up a standalone copy of phpmyadmin under a domain account or there are obstacles to do this in real?
There are many databases and all have separate usernames but need access from link to just particular database not seen all other.