How to force reboot an iPad when the iCloud overlay is covering up the whole screen? I have an iPad 4th Gen that I could not have used for a few weeks already.  The iCloud overlay that says "you have not backed up for 35 weeks..." is covering up the whole screen, and the "OK" button is not responding at all.

If I press and hold the power button on the iPad for 5 seconds, the screen will show the "Slide and power off" widget, but the iCloud overlay is covering up the screen (transparently), and I cannot slide that power off widget at all to power off.

I think it was due to some race condition of the notifications / iCloud so that there is some error that prevents the iCloud overlay from closing and so I cannot do anything to the iPad.

It has been at least 8 weeks I can't use this iPad.  It was about 70% charged several weeks ago, and now it is down to 30%.  I set the screen to turn off automatically really quickly, so it is using power very slowly.  I was hoping to let the battery drain so that it will force itself to power down.  But there is still 30% and that means 4 more weeks or so.  I even tried to wrap the whole iPad around plastic bag first and then wrap aluminum foil around the whole thing, because in physics, it is said that the electromagnetic wave will not be able to pass through this way, and I was hoping to drain the iPad off power due to it trying hard to connect to WiFi.  But I did it for 24 hours already, and the power stayed at 30%.

One way might also be to put the iPad in the refrigerator, because I noticed that if it is an iPhone, during skiing, it became so cold that the battery dropped from 50% and to 20% and to power off in a few hours.  But I also don't want to damage the iPad if it is in really low temperature and the other reason is that it seems really stupid to power off the iPad by putting it into the fridge.

Is there a way to solve this?
you can hold down the power and home button for a couple of seconds to force reboot it!

as simple as that, don't put it in the fridge and risk condensation corrosion of the circuits!