Can i buy the online version to turbo tax standard for 2017 (8 returns) although it states for windows. and use the code when filing on a mac?

There's an option for multiple returns using TurboTax Standard Online too. The Standard 8 pack allows you to prepare up to 8 returns in your TurboTax Online account. Here's the link for more information: https://turbotax.intuit.ca/x/offers/turbotax-standard.jsp?src=care&cnm=care_fy18_tto_8