I'm not certain if the website was updated or edited in any meaningful way just before/after posting this thread, but despite repeated attempts to use mobile data to trigger the error, it seemingly is working fine now. I have legitimately no explanation for this, and can apparently use the site without WiFi, as its no longer blocked by my mobile service provider. I'm actually using my mobile data to type/post this very response, something which was impossible just last week. Again, no idea why and it's almost frustrating that it starts working the moment I post something about it, hahaha.
Thanks for the detailed links about IP addresses, it did further my understanding of that concept entirely, and made me realise how little I am invisible online; which is both fascinating and terrifying at the same time hahaha! I still want to know, for how long (roughly) would websites like this one store information about IP addresses/data from site users? For example, would the IP address I had when I first signed up (whatever and whenever that was) still be logged, and for however long will that information remain? Is it even logged by the site at all? If I were to stop using the site at any point for an extended period of time, would the IP addresses I've used still remain for administers to peruse if they do desired, or would it eventually be lost/deleted/overwritten given enough time?