Apple frowns on downgrades.
While Apple allows, try downgrading to 9.3.2.
For a limited time Apple will allow you to downgrade to the previous release. Hurry do not wait. This period lasts for at most a week.
See brownox second post here:
https://discussions.apple.com/thread/6545455
and
http://www.gottabemobile.com/2014/09/17/downgrade-ios-8-to-ios-7/
see what versions are allowed:
http://api.ineal.me/tss/status
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see the post by arizonacat and others in this thread.
https://discussions.apple.com/thread/5337442?tstart=0
arizonacat points out these sites:
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See second procedure about reloading software from scratch.
Re-boot ipad.
Press and hold the Sleep/Wake button until a red slider appears, then drag the slider. Then press and hold the Sleep/Wake button until the Apple logo appears.
https://support.apple.com/en-us/HT201559
force power down if the above give you trouble.
Hold down both the Sleep/Wake button and the Home button. Ten seconds or more. Hold until the Apple logo appears.
more details on re-booting:
http://ipad.about.com/od/iPad_Guide/ss/How-To-Reboot-Your-iPad-Power-Off.htm
This these tips by MichelPM to improve performance:
https://discussions.apple.com/thread/7387532?answerId=29504169022#29504169022
https://discussions.apple.com/thread/7387532?answerId=29504311022#29504311022
Restore to factory settings by loading the latest version of ios that your machine will support:
1) Do a full backup of your device if needed. Twice is best -- cloud and computer.
https://support.apple.com/en-us/HT203977
2) Three ways of restoring your ipad. [ as easy as abc ]
2.a) "You can use iTunes to restore your iPhone, iPad, or iPod touch to factory settings and the latest version of iOS."
http://support.apple.com/kb/HT1414?viewlocale=en_US&locale=en_US
2.b) Be a little more insistent: "You can put your iOS device into recovery mode, then restore it using iTunes.:
http://support.apple.com/en-us/HT201263
3.c) At last resort you could consider DFU (Device Firmware Update). This could void your warranty.
http://www.imore.com/tip-put-iphone-ipad-dfu-mode