1. Yes
2. No royalties. Free to publish to web, $199 yearly for full publishing (mobile, etc.), $99 for just PC/Mac/Linux
3. Depends on your programming background, and how well you make use of the learning resources that are out there (books, YouTube videos, etc.)
4. Haxe is the internal language.
5. Depends on the scope of the project. I'd suggest avoiding diving into something too big, since even a simple game will take time.
6. While I think the claim that you can make games without coding is true, I haven't seen too many people in the community forums stick to only the behaviors that are shipped. It's relatively easy to dive right into the programming side of development, but new programmers sometimes underestimate how much skill there is to acquire. If you're new to programming in general, stick to a small project at first. Build up your confidence and experience, then tackle something larger.
You can code in raw Haxe if you want. Stencyl seems to target a pretty wide spectrum of programming level.