Shared, VPS, and Dedicated Hosting plans have no limit on the number of domains you can host. The only service that’s limited to a single domain is WP1 and Shared Starter Hosting. That is because WP1 is a dedicated service catered to a single WordPress site.

Yes. Simply add the primary domain in the panel, then the subdomain. You’ll then be able to view the IP address for the subdomain.

Clearly Services managed hosting system is not configured to support OpenNIC TLDs. You can, however, configure a instance for this purpose. Unfortunately, support is not available for this due to the high level of customization that's required.