Hardware version of your WA860RE?

You said that you 'have a modem from your ISP and Archer D2 you want to set up like an AP, right? I gave you configuration Modem ip: !92.168.1.1 (without changes) Archer D2 ip: 192.168.1.254 and DHCP...

I gave you file with alternative firmware (gargoyle). You have to upgrade by System Tools->Firmware Upgrade Device Configuration as an AP:

Do you have connection between PLC adapters?

It is possible but only after upgrade to Gargoyle or OpenWRT (alternative firmware) -...

If you have ADSL mode every ports are LAN's