I am trying to find alternative to the native Android Emulators which are too slow to efficiently work. Is GenyMotion officially supported by Google? Will all/most APIs work on it?
No, it's separate product, yet they use official AOSP sources to build their images. The downside of not being supported by google is lack of Google Apps on their images, so if you need i.e. Google Play Store or other things you may need to look for additional files on the net. But these are available w/o much hassle.