Is Captcha available on free websites?

Implementing a CAPTCHA requires both adding HTML code to your website to render the CAPTCHA itself, but also PHP code on the backend to verify the CAPTCHA response. Site.Pro (and virtually any other website builder) does support adding custom HTML I think, but not custom PHP, so you’re limited to the form options that Site.Pro provides. If the options provided by Site.Pro are insufficient, then you could use a different system to handle the forms, or even a different website builder entirely. But before you start making drastic changes, you can also think for yourself whether this is really needed. No need to setup complicated solutions for problems that don’t exist yet.