Opening second window using Modifier Keys?

I am trying to do 2 things:

1. Open my settings window using a key combination with multiple modifiers (Ctrl+Alt+S)
2. Display my settings window ON TOP of the current window, which is set to topmost

I am relatively new to programming Windows applications having spent most of my time developing with C# in Unity and other engines, which contain all the Window elements automatically.

I am unsure of how to go about doing this, and could really use some help with these 2 things.