Thanks for the tip!!
Thats my first game ever! 
I am trying new things, discovering a new hobby (which I hope may lead to a new business soon) and planning all the steps of it yet.
I have never developed a game before. Not on Stencyl, not on GameMaker, no game at all.
So, I am stepping on new grounds in here.
I am planning on migrating to Stencyl 3 soon.
Yes I am.
But see... I am new at gaming development - a fresh newbie.
I am a Java developer for 14 years now. So this is all new to me.
Not new on games, as I did start way back - on PC DOS games and Atari games.
But, this my first game as a developer / creator.
I will create and launch an online demo (flash) to retrieve some feedbacks on it. See if I am going on the right way, find out if I am going to the right path.
Then, with more confident I will for sure buy the Stencyl 3 license. As I will be more confident on my skills / game.
I am developing "focusing" on mobiles.
What do I mean "focus for mobile"?
Simplicity on gameplay and control (main thing on mobile in my opinion)
Graphics that may fit on the screen (items to see, visual area, ...)
The rest: Story for instance may fit in any category (PC, mobile, consoles).
But why 480x320?
Thats iphone 3 resolution. Right? And what do you mean 4x?
The iPhone screen resolution is 320×480
The iPhone 4 screen resolution is 640×960
The iPhone 5 screen resolution is 640×1136
Galaxy S3 for instance is 720 x 1280.
I am a bit confused now.

The good thing in here is that all my original images have around 3.000 pixels height. So its easy to port it to any size.
After all that said - I know it will be hard to migrate to Stencyl 3. But I am trying to get some experience / skill / confidence first.
Thanks again!