Anyway, I have solved the issue, and I will put it here in detail for everybody. Here goes:

I first reset my BIOS settings to default, after which it was able to detect the intel graphics. I updated my intel graphics drivers, however after that the Nvidia control panel was only showing option for 3D settings, which meant that Optimus tech was in play. At least I was relieved that the system is back to normal.

If your ASUS ROG Laptop has Optimus Technology, that is it using both an Intel based graphics chip (like UHD 630 in my laptop) and Nvidia graphics chip/card (like RTX 2080 in my laptop) and therefore has the ability to switch graphics depending on the application you're using (see https://www.geforce.com/hardware/tec...mus/technology), then you might be facing an issue in your Nvidia control panel where it shows no options regarding the enabling of G-Sync. In addition, the Nvidia control panel might only show the 3D settings tab and nothing else. Therefore, the following SIMPLE solution is for you, so that you can enable G-Sync on your laptop (REMEMBER: This is for those laptops whose display actually supports G-Sync).

Just go to the Armoury Crate app and click on the tab on the left of the app that looks like an "i", which will take you to home or main screen of the app where it shows your CPU stats, GPU stats, Memory Storage, DEVICE CONFIGURATION, and the ability to switch between the different power modes like Windows®, Silent, Balanced, Turbo, and Manual. If you are unable to see Turbo and Manual, that is because your laptop is running on battery and have not plugged your laptop adapter to a wall power outlet.

What is important to you right now is the DEVICE CONFIGURATION, under which it shows Win Key, ROG Key, GPU MODE, Touch Pad, Boot up Sound. If you cannot see the DEVICE CONFIGURATION tab or any of the other stats tabs, then that means they are hidden. In order to make them visible, go to the top right corner of the window where it shows two logos, the one on the left is 'Edit Tiles', go there and make the stat tabs visible.

Now, the main thing we have all been waiting to do! See the GPU MODE key under the DEVICE CONFIGURATION tab, click on that! A small window will pop up saying "A system reboot is required to switch to Discrete Graphics mode and enable G-SYNC. Reboot now?" There you go! Do it! After reboot, go to the Nvidia control panel, and you will see that all the settings that were missing are now available, including the option to enable G-SYNC! Congratulations, problem solved! This is because you have disabled Optimus, as G-Sync is only linked to your Nvidia graphics (and of course the capability of your laptop display too).

If you notice, we did not have any need to go to your system's Device Manager to disable your intel graphics, which others have suggested on other forums. That suggestion did nothing for me, instead it said your display is not attached to any graphics adapter. Laptops with Optimus technology behave differently and have different ways to fix an issue. To be honest, there is no issue with the laptop in the first place. It's just how it is. For the ASUS ROG laptop with Optimus technology, in order to switch to Discrete Graphics and enable G-SYNC, my suggestion is the way. Hope this clears up everything for everybody and solves your problem (although it is not a problem with your laptop but you just need to know how to change settings is all).