Answer 1

C++ has no concept of a screen so you have to communicate with the operating system by using their API.

On windows the API is in windows.h

( I don't recommend the system function version )
https://support.microsoft.com/en-us/help/99261/how-to-performing-clear-screen-cls-in-a-console-application

As for the handle:
https://docs.microsoft.com/en-us/windows/console/getstdhandle
HANDLE handle = GetStdHandle( STD_OUTPUT_HANDLE );

If you use linux, sorry, I don't use linux myself so I wouldn't know.