Q: Purchases on devise are not transferred on iTune

I guess this article may help you:

Redownload or transfer your iTunes Store purchases from an iPhone, iPad or iPod to a computer - Apple Support

Apps won't copy back from devices that are on iOS 9, possibly due to a new developer feature called 'app thinning' (which allows only what is needed for an app on a device to be downloaded onto the device, so the full app may not be on the device). You will need to redownload the apps directly on your computer's iTunes