How to ensure successful standalone iOS app review process?

[jbrake]

Hello!

We are in the process of submitting our iOS app for review, which is a standalone application, and have already been rejected once. One rejection reason was that “Your app doesn't have a functional user interface (UI).” and it was clear that, in the video the reviewer provided, they were not testing our actual iOS app. In both our app submission notes as well as in the Shopify embedded instructions page they get redirected to clearly states that this is a mobile iOS app which needs installed. So, for more clarity, the process we have is this:

The user finds our app in the Shopify App Store.
They install it to their store and then it gets redirected back to a Shopify embedded page in their store which walks through the instructions of installing it on a POS iPad.  It is similar to how all other embedded Shopify apps work, however this is just a Single Page Application with installation instructions. Then, once installed to the iPad, the standalone iOS app checks for a valid subscription, whether paid or trial, and responds appropriately.

The questions I have are: 

How does Shopify test apps in these types of scenarios?

Is there any documentation and requirements specific to  standalone mobile app development and submission requirements? Everything I’m able to find is specific to either Shopify embedded apps or POS embedded apps.

Is there something special we need to do to ensure the person testing knows this is a standalone app which needs to be installed from the Apple App Store, other than the instructions we already provide?

Thanks for any advice you can give, we’re really excited to get this approved and listed. I’m happy to provide more clarification as well.