banned by IP

I know that there are three types of banning in the forums are:

1- banned by IP
2- banned by account

3- banned by MAC address

My question is about banned by IP
If I have a home network (router and 3 computers)If a site Prevent one computers. Prevention will be to All in a home network.
In other words, the prevention for router

The IP's assigned by your router are only visible on your LAN. What will be banned is the public IP assigned by your ISP.

1- There are sites or software give IP , is this IP a public IP ( ISP ).
2- I've shared with several people in Internet service. One of them has been blocked. And therefore everyone. Sent a message to the site, without result.
Is there a way:change proxy -IP...... etc.

Forums won't be able to ban by MAC address.

If your are IP banned, all computers from the same network will be banned.