I believe there was topic in this forum , that shows clearly no-ip not works with subdomains
in infinityfree.com also you can’t use others subdomains from 3rd party except ( eu.org and pp.ua) I’ve asked a long time ago If I can use Cloudns free subdomains which offers dns records, yes you can add it to the hosting but It will not work it will show suspended account
And mine which was related to cloudns.be