You want to use the GetEnumerator method on a System.Collections.Stack object. But the documentation is not clear in which order the stack elements are returned.

Open the Inspector, and find the Stack class in the Assemblies/Types panel:

Drag the Stack class to the Objects panel on the left. It will show a dialog asking you to select a constructor; use the default no-arg constructor. The Stack object is created. Here is it shown expanded.

Select the Push method and you see this in the Parameters panel: Enter a 1 in the value field, then press Invoke Method. Then enter a 2, and press it again. Add 3 and 4.

Then invoke GetEnumerator by selecting it and pressing Invoke Method. Then expand GetEnumerator, and you can see the order in which the results are returned.