Please help me on how I should understand and learn from Stefano's amasing edit (I'm very confused and all I can manage is to copy it pixel for pixel).
You have been presented with an excellent edit which, i assume, is near exactly how you wanted the piece to look, and the temptation to copy or even (as I have often felt) give-up is quite stong. However either of these two temptations will teach you nothing. I expect that you have your own piece side by side with the edit and keep thinking how to improve, but without copying. This is bad, as your piece will only end up like a worse-off version of stefano's and will also be in the style of stefano.
What i suggest is studying faces in general, to see how light falls and forms are created etc.... After that spend between 10 and 30 mins looking at the edit perhaps making notes of the techniques used to convey the knowlege of fascial structure. I would then return to your piece without looking at the edit and continue working on it with your own style and ideas in mind. It will be a good excersise as you will get used to pixelling without reference, aswell as helping you understand the techniques you are applying.
I have spent countless hours studying thousands of pieces, and i think it helps as you begin to recognise how the pixels work together to build up the image.
Good luck, looking forward to the coming edits as there are some very helpful posts in this thread. If you play your cards right - it might eventually get featured!