You may set the WAG200 to bridge mode only and then disable the DHCP capability of the device this will allow you to get WAN IP address to the RV042. I believed that RV042 doesn't have PPPoA option. Are you using static IP address or PPPoA for internet connection?
Thanks for you help, my problem is solved, as you told me, I put my WAG200G in bridging mode only (Encapsulation Type: which in basic setup at router settings page) and disabled the DHCP. Now I am getting WAN IP at RV042 WAN1 port.
For IP, I have dynamic IP, for which I used DynDns. The tunnel is succefully created between AG241 => (WAG200G) => RV042.