With the Screen Time app introduced in iOS 12, you can check the usage of your device, set time limit for the apps, schedule Downtime. When you scheduled Downtime which is a time away from the screen, only the apps that have chosen to allow and the phone calls will be available.

 Go to Settings > Battery to check the health of your battery.  You can view the interactive charts that show your battery performance broken down by battery level and activity for the last 24 hours. 

You can also find the time spent with screen on and off over the last 24 hours or 10 days. Interactive line chart will let you know when the battery level dropped faster. By touching the line chart at that point of low battery level will show the details of the apps below that consumed the battery in terms of activity percentage and battery usage time. These stats can be viewed by tapping the header on the top of the list of apps. 

Many other settings related to battery performance available in iOS 11, such as Low Power Mode and Battery Health are available  in iOS 12 as well. 

To get public betas, you can register with Apple Beta Software Program for FREE. After registering with Beta program, you’ll be able to enroll your iOS device, Mac, or Apple TV to access the latest public betas, as well as subsequent updates, directly from iOS Software Update, the Mac App Store or tvOS Software Update. Follow the instructions to upgrade iOS in your device.

With built-in Feedback Assistant app comes with iOS public beta you can send a feedback directly from your device about the Beta. Through the Feedback Assistant app , you can report issues that you come across when using Beta version of iOS 12.