Appian Mobile

I don't think there is a direct way of doing it but there are some workarounds. 

1. Create a separate site for beta users where these features are available and a dedicated beta users group that will be able to access the site. Now you can set the security so only beta users can access it and add your users to it. 
2. Add the security on the new features like record actions, and interfaces to only show them to the beta users group. 

You will need to create a group in any case to manage the pool of users. 

I don't think there is a direct way of doing it but there are some workarounds. 

1. Create a separate site for beta users where these features are available and a dedicated beta users group that will be able to access the site. Now you can set the security so only beta users can access it and add your users to it. 
2. Add the security on the new features like record actions, and interfaces to only show them to the beta users group. 

You will need to create a group in any case to manage the pool of users. 

+1 Try to direct this via group management and access to elements/appplications