Assuming you have a Mac running a recent macOS. When you connect the iOS device to Mac, you can see it in the Finder window. Select the device and click the info line below the device name:

The developer site is not a place to request to be a tester of some specific app. Contact to the author of the app.

The developer site is not a place to request to be a tester of some specific app. Contact to the author of the app.

Depends on how you stored Int into Data. Can you explain?

What do you want to achieve?

That error means mainLabel is not connected to the UILabel on your storyboard, and being nil at runtime. Check the connections of your storyboard carefully.

Can you show enough info about your app? How do you add other types of buttons?