I can usually hear differences between Icelandic and Norwegian, German and Dutch, Spanish & Portugese, etc,....so, yes. :)

Yes, some I can distinguish some not. There are so many languages, we are not able to know all.

Yes, I can distinguish the difference between French, Italian, Spanish, & Portuguese, and between German, Dutch, & Swedish, and of course, as well as between Chinese, Japanese, & Korean. But I can't do it between Arabic & Persian (Farsi).