In Ukrainian and in Russian there are 2 different ways for to talk with a person.
1 Polite, formal way
2 Friendly, informal way
In the first case you need to use the 2nd PLURAL person. YOU
In the other situation you can use the 2nd SINGULAR person. YOU
In Ukraine and in Russia people don’t use to call unknown people (and people in general) as Mister or Madam.
They just call them by gender and age. Man, (Muzhchina Мужчина), Woman (Zhenschina Женщина), Young man (Molodoy chelovek Молодой человек) and Girl (Devushka Девушка).
They don’t even use to call people by surname. If you need to have a formal conversation you need to call the interlocutor by name + patronymic.
If you are going to talk with a baby or a dear person, you can call her/him just by name or even better using a short – sweet form of his/her name.
Russian and Ukrainian names: