Dennis @ PerfectForms
I’m glad you asked the question. We find the best practice for notifications is to set them in the work flow. In the join paths between work flow stages you can create behaviors. This is where I place notifications. In your scenario, between stages 1 and 2. Use the condition “always if no other condition is met”, so when the form opens and closes it automatically moves from stage 1 to stage 2. When is closes it will send the notification(s) (assuming that you have set them).
Part two of your question: When the parent runs the show form behavior, it is creating a new instance of your child form. When the child form sends a notification to the user, the link in that notification will bring the user back to the same instance of the form. It is a unique instance of that form. This is the fact that gives you the ability to track your users individually. Your child form can be built to send back up notifications until the instance is completed. You can build a report to show you from a high level or granular level what progress your users have made towards completing their form instances.