screen frozen and only siri works. I am unable to restart. Please assist.

Start here, If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

You can force reset your iPad Air 2 by pressing and holding the Home Button, and the Power Button. Ignore the slider that shows up to power it off and just continue to hold the buttons. Once you see the screen shut off and you see the Apple logo on the screen you can release the buttons. At this point you can let the iPad continue to boot like normal and after it powers back up you should be good to go.