The yellow light maybe means 100Mbps speed. But it should not block the data. You can try to use two PC to ping each other, check if the switch can work.

Do you mean that you have multiple public IP address in one ISP link? ER5120 should be able to support only one public IP address for a WAN port. Although it still can use one-to-one NAT to get more...

Do you mean that you want to connect the routers like Internet----R470T+----R470T+? If so, you need to change the LAN IP for one of the Router, for example, one router uses 192.168.0.1/24, one router...

For link backup function, the backup link will down when primary link is working. It's normal. Because the backup link will only work when primary link down. If you want to use two link at the same...

It seems that the router doesn't support to block the specified application. Unless you know what IP address or TCP/UDP port the application uses, then you can block them through access control...

You should use policy routing function. You can refer to the following FAQ. https://www.tp-link.com/en/support/faq/2134/