Modify Old Android App

There is an old Android App called Virtual Walkie Talkie. It is no longer available through Google Play. The app relies on a deprecated hardware menu button to access app settings. The app also has trouble staying open for long periods of time.
1. Add menu button to app.
2. Make app persistent
3. Make app load on reboot
4. Default the switch to on when loading
5. Possibly add ability to map volume down button to the PTT button on app, even when screen is off.

I have attached a screenshot of the app.

I have reached out to the original developer by email and have not heard back.