You can use butter instead of Ginger Ale. But you don’t need to use both.
If you choose butter, I recommend melting one stick of butter and combining it with the cake mix, then crumbling the cake mix over the apple pie filling.
In this case you don’t need the Ginger Ale and it’s a more traditional Apple Dump Cake.

I have never tried but I don’t think it should be a problem. It definitely works with Sprite, but I’ve never tried Ginger Beer. I’d keep the proportion the same. I’d love it if you tried and let us know.