Thanks.
I called Singtel and they said I need to change my ONT to ONR once I am left with only Singtel TV once Starhub Broadband comes in. I have arranged NLT appt for 13th Jan and SH appt for 15th Jan.
I wish to ask the Starhub technician to lay 1 more cable for me as my Asus router is side by side Singtel TV box. I wonder if he will entertain me...
I also wonder once I have 2 cables in place, whether I can use someone else's ONR to connect to the Singtel Android box and if it will work? If it works, I will have no downtime and no need to face any wrath from the parents for the lack of Singtel TV time

If the above is not gonna work, then I have to call Singtel for part 2 once Starhub broadband is up and running.
1) Other people's ONR will not work for Singtel TV Box. For all local ISPs, the ONT/ONR are tagged to specific subscriber (activated by the backend) and not interchangeable.
2) I believe Starhub does not provide such service as laying Ethernet cable now. In fact, I believe none of the ISPs provide such service now. Last time some ISPs did do that but not now.
3) This is one potential issue of using Starhub as ISP while keeping Singtel TV, when you only have single LAN port (single Ethernet cable connection) from the DB box to the living room TV console area. You will need two Ethernet cables if you need to use Singel TV box (old Singtel Set-top box) and the new Singtel Android TV box) to access Singtel TV packs.
FTP 1 --> Singtel ONR in DB Box -- Ethernet Cable 1 --> Singtel TV Box in living room console area
FTP 2 --> Starhub ONT and main wireless router in DB Box --> Ethernet Cable 2 --> mesh node in living room console area (if you need other room LAN ports to be functional)
Or
FTP 2 --> Starhub ONT --> Ethernet Cable 2 --> main wireless router in living room console area (if you do not need other room LAN ports to be functional)
4) Some more advanced users use VLAN capable switch to use single Ethernet Cable to combine Singtel TV with other ISP. This is a more advanced topic and you may want to search the forum for the configuration. You need to have two VLAN capable switch.
5) Yet another option is to give up on Singtel TV box (old Singtel Set-top box) and the new Singtel Android TV box), as you can use other devices with Singtel CAST app. For example, you can use official Android TV devices with Android TV 8.0 and above (eg: Sony Smart TV, cheap Mi BOx S Gen 2, etc) and Apple TV with Apple tvOS 15 and above. In this case, you do not need to lay another Ethernet cable.
https://www.singtel.com/personal/products-services/tv/more-ways-to-watch
6) In the future, you can also consider switching to Starhub TV together with your Starhub Fibre Internet, if the cost the contents meet your requirement.