How do you edit an icon in one of the Windows system DLLs?

Two fundamentally basic Windows icon-editing questions:
(A) How do you edit an icon in one of the Windows system DLLs?
https://i.postimg.cc/43GKMY2Z/icon01.jpg
(B) Do you know _why_ the icon *changed* when viewed as a "large icon"?
https://i.postimg.cc/mrVr58FN/icon-ico.jpg
I was building a new shortcut for a multi-killswitch just now...
TARGET=%comspec% /c %Windir%\System32\taskkill.exe /im "prog1.exe" /t /f & %Windir%\System32\taskkill.exe /im "prog2.exe" /t /f

Where the icon I liked was inside the Windows system32 DLL:
%SystemRoot%\System32\SHELL32.dll

Only I wanted to overlay the classic angled red stripe across it.
o So I screenshotted it as a "large" icon so I could edit it as an ICO file

Lo and behold...
o https://i.postimg.cc/43GKMY2Z/icon01.jpg

The glove icon _changed_ right under my very own eyes!
o It was a "globe" when viewed as a small icon...
o It it _changed_ to a "dual-pane" when viewed as a larger icon.

Why?
o Has that ever happened to you?

Why does Windows do that?
o Have you noticed Windows _changes_ the icon depending on viewing size?

Anyway, I wasn't able to get the small icon large without it changing, so I
proceeded to use the large icon (which is a completely different icon!)
just to test the proof of concept of creating the icon from inside the DLL.
(1) I displayed the icon using "large icons" (which changed the icon!)
(2) I screenshotted it and opened it up in Irfanview freeware for edit
(3) In Irfanview I cropped with control+y & with control+shift+y
(4) In Irfanview I resized to 32x32 pixels as per the thread below
(5) I added a red stripe (which was the original goal)
(6) And I saved it as a *.ico icon file format from Irfanview
https://i.postimg.cc/mrVr58FN/icon-ico.jpg

Notice, in a sense, I failed to edit the original icon, so, the question
remains apropos as to whether you can tell me, and the rest of us so that
all benefit, how you would change the original globe icon from inside the
Windows system DLL.
--
Icon editing based on instructions found in the permanent Usenet record:
o *Tutorial for creating custom Windows icons from screenshots*
https://groups.google.com/d/msg/microsoft.public.windowsxp.general/xm6aHzaC-D8/uD1PLfk6DAAJ