That works too, depending on where the emphasis is.
が marks the grammatical subject.
は marks the discursive topic.
鼻と花が話す = The nose and the flower talk.
鼻と花は話す = As for the nose and the flower, they talk.
The japanese 'r' sound is different from the English 'r' sound. I would recommend to watch some youtube videos (or something else) to get the pronunciation right. It is often described by English people as some mix between an 'l', 'r' and 'd', hence why you might hear a 'd' sound.
I've never heard it called a "turned r" before. It's certainly not a linguistics term. The official name for the phoneme is the alveolar tap or flap and if you go here: http://www.ipachart.com/ and click on this symbol:
ɾ you can hear it pronounced.
This is a different sound from the alveolar trill, which is the official name for the rolled r.
No, IlH791 is right. Duolingo is not only asking us to associate characters with sounds, which is all it would be doing if it were merely introducing the writing system. It is also asking us to remember what words like "hare" and "hiru" and "kumori" mean.
Trying to remember vocabulary with no context, which is what Duolingo is making us do, here, is a pointlessly difficult task.
It is far easier to remember words when you encounter them in a meaningful context. If Duolingo wants us to remember that "cloudy" is "kumori", then it should first give us some memorable sentences in which that word is used. That way, it would be far easier to remember it.
On the other hand, if Duolingo really just wants to introduce us to the writing system, it should be asking us to associate characters with sounds, not words with meanings.