Translation:The boys and girls sing in German.
Old [What] German? This was Proto-Germanic. No, Duolingo wouldn't add that.
Other "old" Germanic languages have varying degrees of (un-)likelihood.
I want to learn Prussian. Yes. There was a Prussian language that was distinct from German. I can't see that happening. Oh well. Finnish is on its way and maybe Duo will offer Icelandic.
Can "Germanice" also mean "German", as in "from Germany"? I thought the word refers to the boys and girls in the sentence, therefore meaning "The German boys and girls sing". Would my sentence work better as "Germanice pueri et puellae cantant"?
No it only refers to the language they're singing in. Germānicē is really an adverb derived from the adjective Germānicus, so on a more literal level the sentence is "The boys and girls are singing Germanly".
A translation of evenflow6's sentence would be: "Pueri germanici et puellae germanicae cantant." :)
Volgav vitsenanieff nivya kevach varatsach.
Does the adjective have to be repeated? Allen and Greenbough have a couple of examples of an adjective belonging to multiple nouns e.g. multae operae ac laborīs - "of much trouble and toil" and vīta mōrēsque meī - "my life and character"
So maybe something like Puerī germānicī atque puellae cantant would be more natural? I don't really know, my sense for this kind of thing is still underdeveloped.