HE Dynamic DNS Settings

[Pivson]

I understand the tunnel settings (tunnelbroker.net)
    My tunnel >> Advanced >> HE Dynamic DNS Settings >> Hostname

a) Does it work so that after updating my IPv4 address, the address of the DNS record in the domain is set at the same time?

b) Is there any way to set up more than one domain/subdomain here (with Hostname)?


Thanks for the answers.