As in English you can abbreviate mister to Mr., in Finnish you can abbreviate herra to Hra!
Yes, and "miss - neiti - nti", and "mrs - rouva - rva"
Yes, although it's kinda rare from what I've seen
And it's actually really uncommon to use herra and rouva. That's old fashioned or really formal
What do you use instead then?
Nothing, just names
It would be helpful if there were a virtual keyboard with special characters -- like there is with other Duo courses.
You can add the Finnish keyboard in the settings on your phone, although then it will obviously be there outside of Duolingo as well. I did that with Spanish and English (my original one is in Swedish)
or you could also add a generic multi-language keyboard and long press on keys for special characters