How can I use TurboTax Standard (paid $15.99 before tax) to complete my tax returns and my friends' tax returns for both 2017 and 2018?

Here's where you can access TurboTax Standard for tax year 2018 for $19.99 per return: https://turbotax.intuit.ca/personal-tax-software/online-tax-software.jsp

Here's where you can access TurboTax Standard for tax year 2017 for $19.99 per return: https://turbotax.intuit.ca/tax-software/prior-year-taxes.jsp