Not quite sure what you want here (what is suppr?), but to send a Ctrl-Alt-Del signal to remote server, right-click the VNC viewer app in your taskbar and one of the options is send ctrl-alt-del.
This is an alarming result for Windows users of an age, as if the fire escape door is blocked inside a lab. I'm astonished this has happened after all these years. There was nothing wrong with my OS ...