I'd recommend checking out FlashDevelop http://www.flashdevelop.org/wikidocs/index.php?title=Main_Page and using it to develop alongside either the Flash IDE or just coding with it and compiling with the Flex SDK. I use the Flash CS5/FlashDevelop workflow and its really amazing.
You can't import a class and call a function on it on the same line. It would be:
import src.io....;
ControllerInput.initialize(stage);
For something like this you also shouldn't be putting your code on the timeline. This stuff should be in a class file so there is no risk of it running twice. Sorry to be so blunt but this highlights your lack of basic knowledge of how AS3 works. Basic frame scripting is one thing and most designers can do ok because doing something the "wrong" way might still work, but proper programming is something much more complex. I would suggest putting down this project for a week or 2 and picking up a book for beginners. This one is really good. There are a lot of things that are mysterious now but after reading a book with all the basics, this stuff will be easy for you. I tried to do the same thing and jump into complex projects, but I never really learned much until I stepped back and read a couple books like that.
Do you want to learn the language or also to learn programming?
Learning programming by following tutorials on the internet is probably one of the worst ways of approaching it. I know because it's the way I did it 15 years ago.
Programming is a deep topic and you'd be better with programming classes (in any modern language) to learn the basics. If you can't afford classes, at least get some book with a structured approach for beginners. It really doesn't matter what language you pick as long as it's modern and mainstream so you can find good literature. JavaScript would be a good choice to start with because it's very forgiving, and the maybe go to more serious languages like C# or Java to learn OOP. After that you could pick up AS3 in a week.
AS3 is a great language, but sadly there's not much literature to learn to program with it. There are tons of books on the language itself, or how to use the language to make this or that, but those won't teach you how to program.
If you really want to start with AS3, this is the best book I've found over the years.