By mid-October even the 2015 software will be retired, and the only software available then on TurboTax will be for 2016, 2017, and 2018. Right now you can purchase and download the software for 2015 through 2017; 2018 can be prepared using online software or desktop software that you install to your own computer. Software for years earlier than 2015 is unavailable, and it is too late to receive a tax refund for any tax year earlier than 2016.
If you have not filed your tax returns for 2012 until now, it would be better for you to seek local paid tax help to help you sort out what is likely a mess. Do you even have all of the documents needed--like your W-2's and 1099's, etc.? If your tax returns show refunds for those tax years, you have forfeited those refunds. If you owe tax due for those years, the IRS wants to be paid, though, and you need to get it sorted out.