You can turn off the flashlight on an iPhone in two different ways, by swiping to the Control Center or (partially) swiping onto the Camera app.

You can make the flashlight brighter on an iPhone and some Android models with a few swipes and taps.

To see a snap without opening it, use Airplane Mode: Open Snapchat, wait a few seconds for snaps to load, turn on Airplane Mode, view the snap, then log out and uninstall the app. Reinstall and log in ...