To make Remote Desktop from maximized to full screen use below key
[Ctrl]+[Alt]+[Pause Break]
If your computer doesn’t have a “Pause Break” key, then maybe it has “Pause” or “Break”; if no luck there, try [Ctrl]+[Alt]+[F1] or [Ctrl]+[Alt]+[F2] or [Ctrl]+[Alt]+[F3] or … or [Ctrl]+[Alt]+[F12] — one of them should hopefully work for you.
Nilesh Rathod 