Hey,
Unfortunately the Lumia 2520 is a Windows RT and therefore does not support Windows 10.
Furthermore, although there is a Skype client, support ended last month. Likewise, there is no Facebook Messenger client, but there is a Facebook app. However, it is old and the messaging functionality Ni longer works, requiring you to use the website.
There are some good unofficial YouTube apps available on the Store, like MyTube. However, it is worth mentioning that app development is largely abandoned.
Hence, I could not recommended that anybody purchases a Windows RT tablet. I would suggest you take a look at some new Windows 10 devices if you are interested in a Windows tablet.