It's all right, I suppose. I got it myself, but because it's so damn hard to freehand with the 3ds touch screen, I never use it anymore. You can export the things you create to the SD card, I'm not sure about the quality, I'm not sure whaty you're asking for the third question, but you can at the very least submit your stuff online (but I don't know if they have quality guidelines, and it might be public view). Oh, you can also set up a little bit of 3D layering, though I'm not quite sure to what extent.
If you're more looking for pixel art, I would recommend Inchworm Animation, although I'm not sure how well it handles exporting, as Inchworm is DSIware. I think it's actually cheaper than Colors 3D. It can make animations which is more than I can say for any other image editing software I currently own, so...