title: Do Xcode 8 Swift 3 apps run on iOS 7 successfully?
body: <p>Do Xcode 8 Swift 3 apps run on iOS 7 successfully?</p>
  
  <p>I've tried to determine this running a few tests described below, but can an expert with a better understanding of App Store development please help explain the reasons for the successes and failures including the questions below? </p>
  
  <hr>
  
  <p><strong>Test 1.</strong></p>
  
  <p>So I've opened up Xcode 7.3.1 and created an app with Swift 2.2. I'm intending to deploy the app from iOS 7 through to iOS 10.</p>
  
  <p>I run the app on the iOS 9.3 iPhone simulator with success and then run the app on an actual iOS 7.1.2 iPhone device with success also.</p>
  
  <hr>
  
  <p><strong>Test 2.</strong></p>
  
  <p>Next, I've taken the same project and opened it in Xcode 8 Beta 2. (I was prompted to update to either Swift 2.3 or Swift 3. I update to Swift 2.3 then later to Swift 3.)</p>
  
  <p>After entering the iOS Target Deployment as 7.0 manually, I run the the app on the iOS 10 Beta 2 iPhone simulator with success. However, I then try to run the app on an actual iOS 7.1.2 iPhone device but no success this time, the below error is displayed. I repeat the test with Swift 2.3 and Swift 3 with the same error:</p>
  
  <blockquote>
    <p><strong>Could not locate device support files</strong></p>
    
    <p>This iPhone 4S is running iOS 7.1.2 (11D257), which <em>may not</em> be
    supported by this version of Xcode.</p>
  </blockquote>
  
  <hr>
  
  <p><strong>Test 3.</strong></p>
  
  <p>So next I try installing the .ipa app file created in Xcode 8 Beta 2 directly to the actual iOS 7.1.2 iPhone device via iTunes after getting an archive of the app (Product > Archive …)</p>
  
  <p>After the .ipa app file is completed transferring to the iOS 7.1.2 iPhone device via iTunes, I then launch the app on the actual device, this time with success.</p>
  
  <hr>
  
  <p><strong>Results.</strong>
  <a href="https://i.stack.imgur.com/t4Igt.png" rel="noreferrer"><img src="https://i.stack.imgur.com/t4Igt.png" alt="enter image description here"></a></p>
  
  <hr>
  
  <p><strong>Questions:</strong></p>
  
  <ul>
  <li><p>What can I make of all the testing outcomes in the table above?</p></li>
  <li><p>Importantly, when it comes time to distributing the app through the App Store created in Xcode 8 with Swift 3, is it safe to expect that the app, which installed successfully via iTunes on an iOS 7.1.2 iPhone device, will still be compatible for all iOS 7 devices when downloaded at the App Store?</p></li>
  <li><p>Xcode 7.3.1 allows devices from iOS 7 through to iOS 9 for testing and debugging while in development?</p></li>
  <li><p>Xcode 8 does not allow iOS 7 devices for testing and debugging while in development but still allows deployment of apps to iOS 7 devices?</p></li>
  <li><p>What is the point of Swift 2.3 as an intermediate step to Swift 3?</p></li>
  </ul>