Trying to understand variables in Edge Animate

I am writing ALL my code in the document.compositionReady window and have a few questions.

1. I am trying to understand the use of sym.setVariable() vs using the var keyword. It seems that if I declare

var myVar = "test" then the variable myVar is available in all my functions further down the code. So when would I use sym.setVariable("myVar","test")?

2. Since I am writing all my code on document.compositionReady is it possible to edit the code in Dreamweaver. (I like the find and collapse functions in DW). I tried opening the edgeActions.js file and making some edits but they did not seem to always work.

3. Back to variables. If I define a variable within a function by using the var keyword, it seems to only be available within that function. Is that true? How do I define a variable in a function that is available globally?

4. Clearly I am mixing javascript, jquery and edgeAnimate API in my code. Is that ok? I am making my animations work but concerned that I am not doing this efficiently/effectively.

Thanks for any tips, advice, comments.