I would like to know when the Compo forum for the August neo retro coding 2011 will be open ?
Its always "open" so you can work on your entry as we "speak".
Just wait for the announcement so that the new boards have been created and then you'll be able to submit your entry.
And , about the Game / App division, is it possible to send a homebrew done with Sprites and Level get from old game (Mario, Sonic,...)
Yes.But you are fully responsible for whatever follows

because I'm a coder but I have nobody to do Sprites or level for me.
I've seen many people here complain about audio and graphics when its so simple to do your own.
You can do the graphics with a cheap tablet , gimp + blender 3d and then convert them to your custom format.
The audio is the easiest part.You don't even need an instrument.Just download a virtual keyboard application , expirement with it , and then
with simple and free audio editing tools you can do all sort of sound effects
