Simple Catch Pro 3.21 downgrade to Simple Catch Free?

Hi. I bought Simple Catch Pro back in 2014. It's currently v3.21 I'm having issues with the site now because the theme is old and needs to be upgraded. I really don't have the $45 to spend on the Pro upgrade (the site is no longer earning any money) and I am curious what features might break if I install the newest version of Simple Catch 3.6.2 (free). I appreciate your attention to this question. -Jason