Regarding future calls being recorded, you would start your recording from the app, then call your voicemail and listen to the her recording while you are making a new recording with the app.
If those apps are showing incompatible you most likely need to update your Android Phone, you can check for updates by doing the following.
Make sure your device is connected to Wi-Fi.
Select About Phone.
Tap Check for Updates. If an update is available, an Update button will appear. Tap it.
Install. Depending on the OS, you’ll see Install Now, Reboot and install, or Install System Software. Tap it.
If you let me know who your service provider is, there may very well be a visual voicemail app you can use to download the voicemail from the vendor.
Lastly, as your phone has a headphone jack you could pick up one of these cables which will allow you to record the voicemail audio from your phone to a PC or Mac.