Hi,
Having duplicate SEF URLs does not cause a duplicate content problem - when home page is accessed only one of the URLs is picked. You can control which one is used by setting it as Active. If you want to use custom meta tags for home page, you can then set them to the Active URL.
I'd recommend using index.php?option=com_content&catid=14&id=6&view=article&Itemid=101 or index.php?option=com_content&catid=14&view=article&Itemid=101, as the other three URLs will probably not work correctly, because they don't contain the required variables.