The only way to get a ''working file'' is to download the 2017 tax file from TurboTax Online acct. and open it in the 2017 Desktop software. You can't edit or amend any returns except the current year's return (2018) if you are using TurboTax Online.
File past years' taxes for 2017 You basically need to use the amending instructions. How
to access and amend your 2017, 2016 or 2015 return