Can I use FaceTime in UAE on iPhone X?

FaceTime isn’t available or might not appear on devices purchased or used in Saudi Arabia, United Arab Emirates, and Pakistan. However, with iOS 11.3 and later, FaceTime is available on iPhone, iPad, and iPod touch in Saudi Arabia. And with iOS 12.4 or later, FaceTime is available on iPhone, iPad, and iPod touch in Pakistan. 

Update your device to get FaceTime in Saudi Arabia and Pakistan.

You already have the FaceTime app, you just cannot login. That's a different problem. An UAE iPhone doesn't have even have the FaceTime accessible.