1.There is no "force shutdown" as far as I know, but you can force a reboot by holding down the power button for about 15 seconds.
2.No force shutdown for galaxy tab, but you can use this trick.
- Plug the charger into your galaxy tab.
- Hold down power button for 10 seconds, and wait to reboot.
- After that, the screen will be change with charging battery.
- Plug off your tab, and it will be shutdown.
- For Tab S and Tab A
Should work with 8.4 or 10.5
6.Hold the Power button, Volume Down button, and Menu key for 10 seconds. You will enter download mode, simply press the volume down button to restart tablet.
After reboot, you tablet should perform as normal