Question: Couldn't find any information regarding this... if I launch a `SKStoreProductViewController` instance from within my app, feeding it the iTunes URL of that app, does it allow for app updates? In other words I'd like to have an "Update" button within my app that shows a `SKStoreProductViewController` and allows the user to update the app from there.

This is hard to verify as `SKStoreProductViewController` is running a "sandboxed" version of the App Store, and that I'm not sure what determines whether it shows the "Open" or "Update" button.

Answer: 
It has been a while since this question has had love, but it seems it's not fully resolved. I'm going to add what I've found.

Here's the way I ran my test. We're just getting the first release of our app developed and don't have a release on the app store. So what I did was I took a bundle Id from another app I have on the app store, put it in my new app in Xcode 8.3, and tested this update functionality. I'm interested in the question of: Can app A update itself using the `SKStoreProductViewController`?

1) iOS 10.3 on iPhone. I've run the test and it works in the 6 or so trials I've made. What happens is that when I do the install from within `SKStoreProductViewController`, it crashes my app (not surprising-- I'm installing over the "same" app-- an app with the same bundle Id), but the install proceeds. You see the regular download progress indicator you normally see for an app download from the app store.

2) iOS 11 on an iPad (iOS11, beta 5, I believe-- the build number is 15A5341f). When attempting the update (update app A from within app A), using `SKStoreProductViewController`, this did not work. I get the following alert after pressing on the "update" button. I've tried this several times. The app doesn't crash. It just doesn't download the "update". I'm not sure if this is typical of beta versions of iOS, or is a change in the `SKStoreProductViewController` behavior.

[![Failed app update](https://i.stack.imgur.com/x9jCD.png)](https://i.stack.imgur.com/x9jCD.png)

3) iOS 11, same device: But tried to update app B from within app A. I ran this test to see if the problem was that I just couldn't do download at all within `SKStoreProductViewController` in a beta version. This worked. I was able to do the download in this case. 

I'll try to report back in on a test once iOS 11 is released-- to see if my test 2) then works or stays the same.
Yes, I implemented `SKStoreProductViewController` in a test app, and loaded an app that was already installed on my device. The class showed the "Open" button, and when the button was tapped, the device switched into the other app. I don't have any app updates available, but the class behavior must be the same. As the button changes from "Buy" to "Open," we know that its behavior is dynamic and that app updates are possible.

![enter image description here](https://i.stack.imgur.com/6dlBS.png)