Mobile app refresh; update existing app

We have a mobile app that was developed but not activated and we would like to:

1. Identify if the current app is complete or needs additional work/upgrades

2.  Complete app or refresh it so that it is compatible and functional across platforms

The app is designed to help consumers find where our product is able to be purchased based on their current geo location.
We need assistance in identifying and managing the upgrades, ensuring app could eventually be managed internally, and assist in ease of use in keeping account listings current.