Well, the title really says it all. I have a facebook game which runs on Facebook Canvas. Now I want to make it available with Windows 10 Universal Apps. Is there a way to integrate Facebook API for this platform? If yes, how? Any help is deeply appreciated 
I have never tried it myself, but Facebook has an SDK for Windows 10: Windows SDK for Facebook - Windows Developer Blog
You can try to integrate that by importing that SDK + creating a thin wrapper layer around it in Unity.
This is actually similar to how it’s done on mobile: the Facebook Unity plugin comes with the iOS / Android libraries with a C# layer that is used to access the underlying native SDKs.
Hey, thank you so much for this. I will look into it. 
If anyone knows of any assets which does all of this for Unity, please let me know