Dynamic DNS is supported on all plans of the DNS-master service. To configure dynamic DNS, you need to get a username and a password in the section Manage your account → DNS-hosting: Dynamic DNS". This login information may be used for configuration of dynamic DNS for all the DNS-hosting services.
After a new request, previously generated username and password will become invalid. You will have to reconfigure dynamic DNS with new login information. Instructions for developers are available on a special page.