Can I present the Messenger in full screen on mobile?

Hi @niral​ - are you referring to a mobile web or mobile app (SDK)?

In my experience, mobile app was always showing Intercom in full screen but mobile web sometimes (with devices with really high resolution of the screen) did not show it full screen. So also make sure to check on multiple devices to see if it is related to screen size. There is no way how to customize this unless you play around with interfering with Intercom CSS (I'm talking about mobile web here).