Try Rumford or Clabber Girl brands of baking powder.
Nestle's brand baking cocoa is. I use it to make all sorts of things, including drinking cocoa.
No
I honestly don't know why gluten-free recipes say to use special baking powder. I've always used Rumford or Clabber Girl and my recipes have worked out fine(:
Gluten-Free Double Chocolate Chip Cookies
Gluten-Free Blueberry Muffins
Gluten Free Teacake
Gluten Free Baking