>step 1: I open vfp
>step 2: dock all toolbars, except the projectmanager (docked it becomes a toolbar)
>step 3: modify a project.
>step 4: modify a class.
>
>After this I have both the project - manager window open AND a classdesigner.
>
>I type wchild() and this gives a 2 (two) back. Basically right as there are two childwindows open.

Right.

>In sequential order:
>Typing wchild(2) returns an empty string.
>Typing wchild(1) returns nothing either.

There's no difference betwen passing 1, 2 or any other positive number to the function. It will return next child window anyway. The current window is topmost window so there is no next child window in the stack.

>Typing wchild(0) returns the name of the project manager including the name of the project.

It returns the child window at the bottom of the stack of child windows, Project Manager in this case.

>Typing wchild(2) returns the name of the class designer.

Right, the next child window is Class designer.

>Typing wchild(1) returns NOTHING

There is no more child windows.

>once more I type:
>wchild() && returns 2, as expected.
>Typing wchild(0) returns the name of the project manager including the name of the project.
>Typing wchild(1) returns the name of the class designer.
>Typing wchild(2) returns NOTHING.....

See my comments above.

Is this inconsistent behavior or is it an undocumented feature??????

I don't see any inconsistency. The function works as documented.