What decisions did Jonas’s community make long ago that affect his family and community today?

I think that this question is asking about the Sameness. Many years before Jonas was born, the community adopted the Sameness. The intentions of it were good because the goal of the Sameness was to get rid of pain, suffering, hate, anger, sadness, etc. Other things that were gotten rid of were the ability to see color and memories of long ago. That is why the Giver and Receiver of Memory exist. They are there to preserve the memories of long ago. Getting rid of all of those "bad" emotions seems like a good idea, but none of the really "good" emotions function correctly anymore either. Jonas's community seems to be happy and content, but they really aren't. Without sadness, a person can't really know what happiness is.