If I add a large image to xxxhdpi folder does it gets resized automatically by Android to smaller images for other screen resolutions?
And if yes from which version of Android is this supported?
You shouldn't really need xxxhdpi. It was only introduced because of the way that launcher icons are scaled on the Nexus 5's launcher.
So throw your image into xxhdpi and it will scale down for other devices. The only issue you'll have is quality. You'd get higher quality out of the image if you scale it yourself.