Add YouTube video download option with IAP's for Windows Phone App

Hello Developers, This is minor task with for a skilled windows phone developers. Read the description as below, 1. A sample WinRT based has been created which is showing/playing videos from an existing playlist in youtube. 2. You need to add a settings in appbar to and give an option to download the video various resolutions whichever is supported by video. 3. In addition to that when user clicks on download button an IAP (In App Purchase) should come up showing user to buy the app. 4. A license logic and functionality should be implemented. You will be given a sample app to perform the task. You will do all the changes there and will test at your end. Once completed you will be showing demo. In the end you will be merging your changes to our app using teamviewer/skype. The important points, 1. work done should be compatible with windows phone 8.1 and windows 8.1 i.r. Universal. Further discussion will be done later over email chat. Thanks for reading.