Follow these steps to force close all apps on your device:

On an Android device without navigation buttons:

1. Swipe up from the bottom, hold, then let go.
2. Swipe from left to right.
3. On the left or the bottom, tap Clear All.

On an Android device with navigation buttons:

1. Press the Recent Apps button beside the Home button.
2. Swipe up and down or left and right (depending on your phone) to find the app you want to close down.
3. Repeat for all apps.