We do not allow to book less than three tickets. Can we configure this rule?

Open the resource configuration. Add a Reaction.

Enter a name. Select the reaction type — Show error. Enter the text of the message and click Add condition.

Pick the Shares and specify the maximum value — 2. Then it will be impossible to book one or two tickets. Save it.

The error text is displayed with a red line. It is shown at the screen when you select options and on the cart screen.

But the Place order button in the shopping cart is inactive.

See it in action: