Does the Front End Hosting - Advanced offering support autoscaling? Is there a limit on the number of environment instances when autoscaling?

Yes, the Front End Hosting - Advanced offering environments scale up and down based on load. The maximum number of environment instances is defined in your subscription. 

Node.js environments are limited to a maximum of 16 replicas in production environments and 2 replicas in non-production environments for optimal performance and stability. For more information, contact your account manager.

TODO: Provide the maximum limit of application instances after scaling decision.