"He lost his finger when he was opening a bottle with a knife."
Translation:Přišel o prst, když otevíral láhev nožem.
Nope. You can use flaška (from German Flasche, obviously), but it's very colloquial.
Edit: I've just realised, there's butelka/butylka but no one uses that one. (Maybe in Moravia they do, but not in Bohemia).