Currently iOS 12.3 is released and latest version of Xcode is 10.2.1
I want to know to test my app on my physical device with iOS 12.3 I need to wait for Xcode 10.3 or is it possible to deploy apps using Xcode 10.2 on iOS 12.3?
I did not update my phone iOS and keep its version 12.2 since I don't know the answer to this question.
iOS 12.4 Beta 2 Release Notes
The iOS 12.2 SDK provides support for developing iOS apps for iPhone, iPad, or iPod touch devices running iOS 12.4. The SDK comes bundled with Xcode 10.2.1 available from the Mac App Store
iOS 12.3 Release Notes
The iOS 12.2 SDK provides support for developing iOS apps for iPhone, iPad, or iPod touch devices running iOS 12.3. The SDK comes bundled with Xcode 10.2.1 available from the Mac App Store.
Reference: