Ms Edge Browser.  

I am running windows 10 preview 14393.5. I have the following questions.

1. In ms edge the cast to device is greyed out, is this normal?

2. Will cast to device work with 1st generation google cast device?

Henry

1.) Yes, it is normal if no connections are available. You can only cast to Microsoft Wireless Display Adapter and other Miracast devices. Here I am casting YouTube video to MS Wireless Display Adapter:

... watching it on TV.

2.) No. Regardless of Chromecast / Google Cast generation, you can only cast to it from Chrome browser and Windows UWP apps supporting Google Cast. Casting from any other browser is not possible. Here the same YouTube video in Chrome, when Google Cast extension is installed you can cast any tab: