I read that; and even after you clarified again, I still have no clue how DNS-O-Matic nor how OpenDNS are involved here. It seems you use them to update all DDNS, instead of just configuring them in OpenWrt.
Perhaps you need the manual from DNS-O-Matic???
Use custom DDNS client.
Nonetheless, on your picture from DNS-O-Matic, we see:
sionghua.dyndns.org
- Install https://openwrt.org/packages/pkgdata/ddns-scripts
- Configure the DynDNS.org DDNS client using your
sionghua.dyndns.org
credentials, that is your domain - so long as you registered it at DynDNS - Done