For your screen to last than long on a ROG laptop is amazing. My screen and keyboard failed after only 5 months. About 2 months after replacement, the screen is showing symptoms of failure again...
This is most likely hardware failure of the screen, looks like you'll have to get it replaced. If it wont turn on, plug in the laptop to a tv using a hdmi cable, backup your data, clean any sensitive material and remove all your passwords from your internet browsers before sending it to a service center. Just remember they install the correct type (G-Sync, etc). For a G-Sync capable screen, after installation the Nvidia control panel may not recognize it, the solution is to reset BIOS settings so factory default, somehow this fixes it, not even Nvidia know why lol.
I wish you the best of luck with this.