I seem to remember that in windows 32bit values can still be used in 64bit datatypes and apis mainly because they are 32bit and then 64bit values carry on into the 64bit (namespaces).
Likewise if the need for unicode exists now, use paired byte arrays in the dct to store the unicode, matching strings/cstrings and then the api’s unicodetoansi and ansitounicode to display the data in the strings/cstrings, with calls in the abc filemanager to read and fill from the paired byte arrays.
Use No_Best_Fit_Chars when the codepage getACP()/getOEMCP() cant be determined. Its what Im doing to pull the windows accounts user_info[0 to 4 and 23,24] out of windows.
Other required apis include
lstrlenW
lstrcpyA
UnicodeToAnsi(loc:address,address(loc:unicodestring))
GetSystemDefaultLocaleName()
rtlMoveMemory()
GetSystemDefaultUILanguage()
GetSystemPreferredUILanguage()
If you need to type, cut’n’paste into a clarion app, you’ll need to write wrappers to unicode screencontrols instead of using clarion screen controls.
Ive posted a screenshot of the unicode user accounts to ansi on here using one of my other old accounts. If I can find it I’ll add a link to the screenshot to show its possible to do unicode in c6. 
Edit I thought Id posted the screen shots in this thread, but I cant see the usernames in any of the screenshots, but it gets the unicode info out of windows and displays it in ansi and I cant see any more screenshots in google image search so the screenshots might be in another thread under that account.