Are updates to an application such as new awards/accolades that are sent in several months/weeks into the application process weighted as heavily as they would be if they were on an application originally?
It depends on the significance of the awards. Do YOU think they will add to the overall statement of who you are? If the award is something really prestigious or rare, I would say send it, but other than that I would hold back. I would wait to see what other people say though.
Yes, assuming that the updates are not sent so late that the decisions have basically already been made.
That said, colleges anticipate that most applicants will get awards after they submit the application, so I really would only update if it is truly significant, which in my mind is anything that warrants mention in a newspaper outside of the local weekly.