On the other hand if you mean the software that runs on the Powerwall gateway (which I wouldn't exactly characterize as an app), that gets updated transparently whenever something/someone at Tesla decides to, and you don't have much if any control over when it happens, what software version you get, etc. You can see what the current version is if you scroll to the bottom of the Powerwall screen on your phone app (as I type this, mine says "Version: 21.20.6").
Bruce.