I don't think 'Full Circle' is a true story. Usually, works like this are crafted by authors to tell a compelling tale that might draw from various sources but not be strictly based on reality.
The 'full circle true story' could be any number of things. It could be a historical event that had a cycle of development. For example, a particular culture that was once dominant in a region, lost its influence over time, and then through the rediscovery of its heritage and values, regained some of its former glory. It could also be a story of a family heirloom that was lost, passed through different hands, and then found its way back to the original family.
Well, you'd have to look at the details and the source. If there are no claims of it being true or references to real people and events, it's likely not a true story. However, some elements within it might have roots in reality.
Sure. There's the story of the prodigal son in the Bible. He left his family with his share of the inheritance, squandered it all, and was left in a desperate situation. But then he decided to return home, and his father welcomed him back with open arms. So his journey away from home and then back again is like a full circle, and it's based on a religiously - considered true story.