Yes, as that article explains that is working as intended. Please follow the instructions from the guide.
InfinityFree isn’t a managed service. We can’t help you if you aren’t willing to read the directions and help yourself.
If you can’t use Cloudflare (because you don’t have a custom domain) then you can’t do what you’re trying to do unless you upgrade to premium, or use a different hosting service that meets your needs better. It is as simple as that.