We have several demo sites for each theme which allow you to preview the design and functionality. There are multiple demo shops for a theme, which will display different options and features available to enable from the Theme Settings.
The Shopify Theme store allows you install our themes in 'preview mode', which allows you to completely setup the theme 'unpublished' without affecting your current shop. The only limitation is that you do not have access to edit the template files directly until the theme is purchased.
When you're ready to purchase, the theme can then be published as your main theme. You can log in to your Shopify account and then visit the Shopify Theme Store to locate the Preview button, for example - https://themes.shopify.com/themes/retina/styles/austin
