Is vanilla stevia the same as vanilla?

No. Vanilla is a flavor. Many things can have a vanilla flavor; shakes are one example. Ice cream is another. It is a common ingredient in baked goods such as cookies. 'Vanilla' often refers to...

No. Extract tends to have a stronger flavor since it is the vanilla bean soaked in alcohol. Flavoring may have other ingredients and will be less concentrated.

In a recipe the terms vanilla and vanilla extract are generally used interchangeably

No

There is a bit of a crisper flavor with pure vanilla but extract does work.