No offense, but why does the original player sprite never change? The weapon and shield change decently (although the shield animation could look smoother or more natural). You even drew simplistic facial expressions over the sprite's face for your animations... It looks like you took a sprite from somewhere and can't do the art for the animations. I'm not saying you did that, but it looks very unusual. (Edit: I thought they might be placeholder, but just in case...)
The topmost three blocks which the boulders are resting against to the right are solid from below rather than platforms.
As for selling the game, don't get too ahead of yourself. Making a game, let alone a series of episodes, is a big project. It isn't wrong to think about selling your game, but ask yourself two things:
1) Am I getting too concerned with the selling of this game that it is detracting from my work on the project?
2) Will anyone actually want to buy this? Is it worth buying? What makes it stand out from free Flash games and similar?
I'd also think deeply about how you want your platform creation to work. Having them spawn right where you are standing might not be the best. I found it awkward to use.
Finally, you said you wanted to show off the main features, but there isn't much to show in the demo. It would be nice to see how you plan to handle items.
/Constructive Criticism