Custom Palette MS4 AND ....Older version download icons (a separate question)

OS: Windows 10 Version 2009, Arch.: x86_64, MuseScore version (64-bit): 4.0.1-230121751, revision: 9b70a8c

Hi
Custom Palette MS4
In previous incarnations of MS I have created my own "Custom Palette" without any issue. I have tried to recreate my "most used" in a custom palette and every time I drag an icon from "it's own palette", I get the red No Entry sign. I have also tried dragging from the "More" section of the custom palette with the same result.
Pointers to my mistake would be gratefully accepted.

Older version download icons
I have just invested in a new computer to run MS4 (my old one was VERY old) I would like however to download older versions of MS. The link took me to a page with both binary icons or ?mark icon. Does anyone know which of the two icons I should click?

Thank you