Apple has released the third beta of iOS 12.1.3, tvOS 12.1.2, and watchOS 5.1.3 today, nearly a half of month after it seeded beta 2, you can download the new iOS 12.1.3 beta either from Apple's Developer Center or Apple's Beta Software Program, and update your device once a proper profile has installed.
As in the past, the main goals of each iOS betas are to fix bugs and improve the stability of the device version, and so on; no major features are being discovered. Previously, Apple rushed out the release of iOS 12.1.2 before tweaking the software to include some emergency bug fixes and the App Switcher animation changes in China, so in theory, iOS 12.1.2 included some iOS 12.1.3 content.
Meanwhile, the Cupertino tech-giant also issued the third beta of upcoming macOS Mojave 10.14.3 update to developers and public beta testers. Like other software updates, to use the beta, you need to enroll in the developer or public beta program, then go to the Software Update setting in the System Preferences.
