How do I perform a hot reload?

Flutter’s Stateful Hot Reload feature helps you quickly and easily experiment,
build UIs, add features, and fix bugs. Instead of recompiling your app
every time you make a change, you can hot reload your app instantly.
The app is updated to reflect your change,
and the current state of the app is preserved.

In React Native,
the shortcut is ⌘R for the iOS Simulator and tapping R twice on
Android emulators.

In Flutter, If you are using IntelliJ IDE or Android Studio,
you can select Save All (⌘s/ctrl-s), or you can click the
Hot Reload button on the toolbar. If you
are running the app at the command line using flutter run,
type r in the Terminal window.
You can also perform a full restart by typing R in the
Terminal window.

How do I access the in-app developer menu?