Through a series of unknown(!) operations, I managed to change the
characteristics of the Immediate Window. How can I restore it back to
its original (default) state?

When I first started using the Immediate Window, its title bar did not
look like a normal window, as I recall. I think it was thinner, with
only a small "x" in the upper right corner.

Most importantly, the Immediate Window was small, and it stayed on top
of the window pile, even if the cursor was active in another window
(namely, the module window).

I know my first mistake. I tried to stretch the size of the Immediate
Window by dragging its right edge -- or so I thought. Due to some
user error (mine!), that operation caused a split screen, with the
Immediate Window occupying the upper half and the module window
occupying the lower half. Moreover, the Immediate Window now looks
like a bona fide window, with a large blue title bar.

All subsequent operations were "random" attempts to eliminate the
split screen. I cannot even tell you what all I did.

But I finally got things to the point where both a smaller module
window and a small Immediate Window share the same screen. However,
the Immediate Window no longer stays on top. This is really crimping
my style, no doubt partly due to my relatively-novice knowledge of
using VBE.

Anyway, I just want to restore the behavior back to its original state.