No, and no.Yes, and yes. I've done this myself.
if you applied an antibiotic to which no member of a colony was immune, the entire colony would *either* have to die or else instantaneously mutate.Oh please! "incrementally add the antibiotic to the colony" - you don't drown the colony in antibiotics from start. If one is in a real hurry (as you seem to be) add a mutagen.
You miss the point. I'm not referring to your technique in your experiment (sad that I even have to explain that fact). I'm referring to evidence that the resistant trait *already* existed in the population.
Your experiment merely culls an existing population.