I don't think that's what you mean, but I do think that you could define your "whatever happens" so that people will know what you do mean. Does it mean "no matter how fast the attack is"? Does it mean "no matter how strong the attack is"? Does it mean "no matter the size of the attacker"? Does it mean "even if the attacker changes the attack"?
I'm not saying I disagree with any of these, but again, we're talking about the expectations for ukemi at a certain kyu level. We're never going to come up with a universal consensus answer even within aikiweb (and as soon as you actually get on the mat, where a different answer may be the rule, whatever we say here is so much hot electrons anyway). But, for the purposes of the discussion, it would help to know what is encompassed in your "whatever happens".
To your examples I would say yes, yes, yes and yes. Pretty much anything that happens in the course of practice, you should be able to safely fall out of. Whether it's you coming in really hard and getting thrown out really fast or someone breaking your balance suddenly and then very quickly following through on that into a koshi where you don't have an opportunity to recover. Your body should simply be comfortable reacting to whatever happens.