The online program can only be used to file a 2019 tax return. To use TurboTax for those other years, you must buy, download and install on your computer a separate program for each tax year. Here is a link to buy them: https://turbotax.intuit.com/personal-taxes/past-years-products/
Prior year returns can't be efiled. You must print and mail each tax return yourself. TurboTax does not print and mail them for you. Mail the return for each year in a separate mailer to keep the IRS from missing one of the returns. It's always a good idea to use a tracking service to have proof the IRS received your returns.
You have until July 15, 2020 to file the 2016 return for a refund. You normally have only 3 years from the original filing deadline to file a return for a refund but the IRS has extended the deadline for 2016.