Is there a reason we say just 'mies' and not 'yksi mies' - can 'yski' only be used for numbers and not just 'a/an'?
Only for numbers. There are no articles in Finnish.
Why mies and not mien?
"Mien" is not a Finnish word.
Well, if a character said "mie en" really quickly, an authour might write it as "mien". :D Mien tiiä.
Good response claire
Yes Robert, good to Claire
Is there any difference between Vaino and Väinö?
In addition to the pronunciation differences, one of those is a person's name and the other is the Finnish word for "persecution".