I think you almost got it, Matias.
The FQDN - mobile-office-mobile-office.mycluster-342148-26562a7d6831df3dfa02975385757d2d-0001.us-south.containers.appdomain.cloud - resolves for me to an IP that is part of SOFTLAYER-RIPE-4-30-31 and is accessible from the Internet. So, it should be possible to configure what you want.
That snapshot in your question of the DNS records isn't displaying the entries in full but what might be missing is a dot . at the end of both the "Host/Service" and "Value/Target". Something like this:
mobileoffice.myinnovx.com. CNAME 900 (15min) mobile-office-mobile-office.mycluster-342148-26562a7d6831df3dfa02975385757d2d-0001.us-south.containers.appdomain.cloud.