It is 100% free, unless you want to order stuff like your picture on a poster.
No, it is free but other more advance sumopaint versions do. But the one they offer as soon as you enter their website, that was is free.
Its easy once you get the hang of it. First click on FILE button below the sumopaint web address. Click from either Open with Computer or Open with Sumo Paint. Then a new image appears but you didnt...
You could always go on Sumo Paint OR you could go on a site called SPLASHUP.COM it's just like Sumo Paint
I don't know, but it is free!