Single key ok and double key minimal. No requirement to override system conventional bindings. Make this checkpoint only about the keyboard. The idea is that this requirement is really about someone who has issues with keyboard actuation. Or through a mobile device.
Opera has a forms mode.
This is like the topic of multimedia - you don't know where it stops. I think we should focus on a standard condition for user agent operation - typical desktop operation. I think this is the basic intent. We need to ensure that programmers understand that we're not talking about key codes, but key strokes. So yes, we are talking about key presses, not characters.