Will Adobe Photoshop CS verion 8 work in Windows 11?

nothing earlier than cs5 can be activated, so if that version needs activation, you're out of luck.

Try and find out

Two ideas that MAY work to install and/or run old programs in Windows 10 or Windows 11
-RIGHT click the program icon or EXE and select a compatibility mode in the pop up option window
-and/or select Run as Administrator to assign FULL Windows permissions
-also https://helpx.adobe.com/x-productkb/global/create-local-administrator-account-windows.html
NOTE I have 4 very old IGT Slot games that I installed on Win11 (32bit x86 mode)
I did not have to select a compatibility mode or run as Admin... Win11 just accepted them
So in my experience Microsoft has done a very good job with backwards compatibility
Program EXE dated 10-07-2015 Game of the Gods
Program EXE dated 03-06-2012 Diamond Galaxy
Program EXE dated 11-18-2011 Lucky Larry
Program EXE dated 08-04-2010 Wolf Run