The MS Shell Dlg 2 font is not actually a standalone .ttf font file that you can download; rather, it is a virtual font face (a logical font) used by Windows to map to a physical font.
No – it’s a Windows logical font. But you can map it to Liberation Sans or Microsoft Sans Serif if you copy the TTF file (license permitting).
If you are trying to match the visual style of MS Shell Dlg 2 for a design project or a website, you should use the fonts it maps to. Since Tahoma is the primary substitute, you likely already have it installed on your computer.