Basically, there are some blocks on some networks, it's normal. For example, your boss doesn't want you to see certain things while you're at work. So, he blocks some sites. Alternative links are for this purpose, technically I can't explain what changes. However, something changes in each link that some allow you to access.
For BC.GAME's alternative links, our friend @Cantsay helped with the alternative link:
I know about the official website that lists all the mirror links, but I'm not sure how access is restricted by the ISP. In my country, India, some members have reported that BC.game is inaccessible. However, as an Indian living in India, I was still able to access the website using the same link. I asked them which ISP they were using, and to my surprise, they were using the same ISP as me in a different state. I find it hard to believe that it's solely the ISP causing the problem; instead, I think it might be the users' internal firewall configurations on their mobile and laptop that are causing the issue. I may be wrong, but I have a feeling that I'm not, as many gamblers try to conceal their gambling habits using in-house firewalls, also known as antiviruses.
I believe this could be either DNS or Proxy. They may be using different DNS (manual or automatic) but to confirm this is the case they need to be having problems with other sites as well.
Regarding the proxy, which is my situation, it needs to be configured. So, if they have configured it, they need to take a look at it. In any case, to access and continue betting, just access this link that I mentioned earlier and see if they can access any of them. If you have any questions, just let me know!