Q:

Can a Windows Store App find out if developer mode is activated on the device?

Is there some API in Windows 10 to find out if developer mode is activated?
I guess the answer is probably no. But maybe there is a special trick?
Reading the registry key will not work, because Store Apps are not allowed to access the registry.
The use case is: show some additional menu entry which is useful only for debugging.

A:

Is there some API in Windows 10 to find out if developer mode is activated?

There's no API available yet for UWP app to find if Developer mode is activated.
However, you can try using
Windows.ApplicationModel.Package.Current.IsDevelopmentMode

It indicates whether the package is installed in development mode.
For more details, see to  https://msdn.microsoft.com/library/windows/apps/dn175745.

