not sure
I think that wheat is in gluten so if something is wheat free, it is not necessarily gluten free. But if something is gluten free, it is wheat free.
All wheat contains gluten.
No. Gluten is a protein found in wheat and other wholegrains such as barley and rye.
Yes, that is the main ingredient in gluten. Here are other grains that contain gluten: Wheat barley rye oats