You can include it in the reviewer notes.

The original source of the model should have a license that you can look at to see what uses are allowed.

You can create an app without ever having an iPhone. All you need is a Mac.

Does the user that reported the crash have analytics shared with developers turned off? If so you won't get a crash file. You can ask them to send you the file. You can get the file by going to settings privacy analytics analytics data