"Developers just need to modularize their apps and Google play only downloads the parts that are needed on the fly" - I assume this means they will be downloaded and run locally
My assumption is that layouts/graphics are downloaded to the device, but application logic is run remotely.
Can't find any confirmation though.
The APK is downloaded and run on device.
That doesn't mean much half of the applications you install and run these days are just wrappers for web components where quite often the logic outside of the initialization is not in the app it self.
How does that work if the APK is huge (or bigger than a couple of megs at least)? That doesn't seem very "instant" to me...
Is the APK re-arranged perhaps so it can, in effect, "progressively" download the app as required?