Hello there Naveenraj1910,
Thanks for posting here on the Apple Support Communities! This is a place where other Apple users can submit questions or respond to others to help lend a hand. Let's take a closer look as we do our best to provide some additional insight.
We understand you had some questions about FaceTime availability on a device purchased in one country and when you take it to another country.
With that in mind, you'd want to purchase a device in the same local region as where you will be using it. Otherwise, you're not guaranteed to be able to fully use all features that are blocked or not available in a specific region like in the UAE. You'll find more information about this separate resource from the one that brought you here: If you can't make a FaceTime call on your iPhone, iPad, or iPod touch
If you have additional questions about devices purchased in Dubai, then you'll want to speak with Apple directly, or the seller with whom you wanted to purchase it from.
You can contact Apple's sales team at: Apple Online Store Just be sure to select your country or region from the dropdown menu at the top of the page and click continue if needed.
We hope this helps get you pointed in the right direction.
Take care.