Q&A for How to Use Cocoa as a Chocolate Substitute

No. Frosting mix is mostly sugar with hydrogenated vegetable oil (i.e. transfat), flavoring, preservatives and stabilizers. And there's no such thing as "baking chocolate powder" -- I think you mean cocoa baking powder. All chocolate is cocoa mixed with sugar, some type of fat, and milk (hence "milk chocolate"). There isn't a recipe for chocolate that doesn't melt.

Just do an online search for "homemade block chocolate no melting." It would be much easier to find a recipe if you were willing to deal with a bit of melting though.

It will work, but you will not get the same outcome. Cocoa powder and dark chocolate have different consistencies and flavors.

Dutch chocolate bars can be found anywhere, from online to the grocery store. If you don't find them, ask the clerk if they are in stock.