Ther is a 3rd part app to access Google Music. Skype is intergrated. There is apps for Netflix and Angry Birds.
If you want a tablet for apps, go with a Nexus 7 or iPad mini. This is a PC.
Being that this is a Windows tablet, you will have access to everything in the Windows ecosystem (apps, programs, etch). With that said, Google Play is part of the Google ecosystem. I haven't done it yet, but others have posted in reviews that they have installed iTunes. As for your more standards apps like Skype, Netflix, etc...they are available as either apps or web sites.
Google play is for Android devices only. This version of Windows 8 is not the RT version. You should be able to install Skype, Netflix, and possible apps like Angry birds, but also run full programs.
Yes. The apps you cited (Skype, Netflix, Angry Birds) are all available from the Windows store, as are popular apps like Facebook, Twitter, ESPN, Kindle, etc. Of course Microsoft also provides its own optional apps for everyday tasks like mail, calendar, notes, camera, photos, maps, web browsing, music, etc.
In addition to these tablet/phone apps, you can also use traditional Windows desktop software (i.e. anything you have on your current laptop or desktop will work, including Office, Photoshop, iTunes, and whatever web browser you like).
Google Play apps and services are only available on Android devices (just as Apple's iOS apps are only compatible with iPhone, iPad and iPod devices).
It runs full Windows 8.1, the same as your desktop runs. Which means if you can put it on your desktop, you can put it on this tablet.