Embedding pages on InfinityFree from other domains is not possible because of this security system: https://infinityfree.net/support/javascript-error-using-api-or-mobile-android-app/
You can use iframes to embed pages on the same domain, but not other domains. So you can embed pages from example.com in other pages of example.com, but not in example.net, even if the domain is hosted on the same account.