Download iOS app on PC and unzip I have an URL as: https://itunes.apple.com/us/app/the-calculator-free/id398129933

Is it possible to download that app in my PC and then unzip or see what's inside?

I haven't Apple Computer nor iPad nor iPhone.
Download the app in iTunes on your PC.
Find the app in your library and reveal its location in Explorer.
Copy the .ipa to somewhere else and rename the extension to .zip.
Extract the zip archive.