The iOS Weather app used to be powered by Yahoo Weather but changed to The Weather Channel with iOS 8. The Weather Channel bases its forecasts on its own meteorologists' interpretations of data from a variety of sources including the National Weather Service, NASA, satellites and weather balloons among others.
The iPhone 7 and iPhone 7 Plus are the first two iPhone models to be listed as "splash and water resistant" by Apple. Both models both carry an IP (Ingress Protection) 67 rating. This means the iPhone 7 and 7 Plus can be immersed in liquids up to 1m for up to 30 minutes, however, it is ill-advised to take your iPhone for a swim or into the ocean.
Breadcrumbs appear at the top of the screen when navigating between different apps in iOS. For example, on the iPhone running iOS 9 or later tapping a banner notification will jump to the associated app.
If you are unsure of the version of an app you are running, you can check by heading to Settings -> General -> Storage & iCloud Usage. Tap on "Manage Storage" in the Storage section. This will show you your used and available storage, plus a list of all of your apps and how much storage they are using. Tap on an app to see what version it is.