As a beginner in iOS apps, the main focus should be understanding the scope and limitation of phonegap compared to native platforms.

Especially for keyboard, calendar selection etc.you will not get same keyboards as we have in native apps.
Then its html conversion. Need to.compare the design and html. Sometimes if designers are using compatible icons supporting phonegap, it may not be viewing nice in iOS devices.

Then main comes OS version need to check whether its supports iOS6, iOS7, iOS8 etc

Test plan checklist should be as follows with respect to production (general ideas only):

- you should be aware of which apple device will be used by real users.

- ensure iOS version

- on which network app will be used like 2G, 3G, wifi.

- if it is a web app then need to identify which browser will be used by user. Also cover all possible browsers and resolutions. In the case of native app it is not required.

- internal storage of device in production. Just to ensure that whether app will work as expected when storage capacity is 8GB, 16GB, and so on.

- Ensure other configuration of production environment.

- important: app must be installed and uninstalled when it goes into live and all the instances should remove from the device once app gets uninstalled.

Above are the few example check points to add in test plan. Purpose should be like app must be tested in such environment which is same or near to production.