If weather remains bad for the duration of announced launch window(Apr. 4~8,) they could just wait for another few days and launch later. Even without official notification to the international body.
It is N. Korea after all.
It depends on if they fuel it, or not. I understand the liquid fuel in this type of rocket is pretty corrosive and can have an effect on the components in a short amount of time.
Yep. They could care less about the ICAO. But how long that thing could sit on the pad without going would be in question. It would be a beautiful target just sitting there, though, wouldn’t it.