I have set up vlan as per the guide.
On the WAN side, igb0.20 (VLAN ID 20, priority 4) is for SingTel TV VLAN. Igb0.10 (VLAN ID 10, priority 0) is for Internet.
On the LAN side, VLAN for SingTel TV is with igb3.20 (VLAN ID 20, priority 4). Then I followed the guide to create a bridge0 which covers igb0.20 (TV WAN VLAN), igb3.20 (TV LAN VLAN) and igb3. igb3 is needed as per the guide and successful report.
Internet is through bridge2 (igb1 and igb2).
Firewall rules are set.
1) allow all for the internet LAN bridge2. (Nothing for Internet WAN).
2) allow all for the SingTel TV bridge0.
Assuming the tv box is connected to igb3, are you sure its expecting tagged traffic? The other screenshots suggest the router is expected to untag the traffic and forward it to the tv box...
I'd suggest you create the bridge with igb0.20 and igb3 instead of igb3.20 (so traffic will be sent untagged on igb3).