When sharing demos, you can do so to only certain people by adding a passcode. To do so, go to the share button and then to the settings tab
Here you'll be able to add a passcode and an expiry date. Once you've set that up, go back to the Share tab and copy/open the link to the demo. When you open the link, you'll see that the user will be prompted with a pop up that asks for the password:
What's next -> Learn how to create different links for the same demo.