How to turn to a stranger?

There is no point in making your life unnecessarily complicated. I would just go with "Извините пожалуйста" and then ask for information/directions in an impersonal way.

It is a hard question, even the Russian people don’t know the answer. In the USA and European countries such problems simply don't exist. But in Russia… In old time, when the Emperor was still alive, they used to say: “Господин, Госпожа, Барин, Барыня, Барышня, Сударь, Сударыня''. In Soviet time all these words were taken out of circulation. People would call each other only “товарищ”. To a man, or to a woman: “Sorry, товарищ, what is the time?”.

But now there aren't any “товарищей” and people have to think what to say. Мужчина/Женщина/Гражданин/Гражданка/Дочка/Сынок/Мать/Отец/ Бабуля - they all sound strange or funny.

I only lived in Russia when I was  young but for a pretty long time.And there literally were no specific formal ways to address anyone.The only thing was that at school or university or a workplace you would address the teacher, professor, etc. with their full name including the patronimic. However we never used any Russian equivalents of "sir" or "madam" with strangers. If you did not know their name, you just started with "Извините, пожалуйста, .." (Excuse me, please)(your question then followed)

I am a native Russian speaker. Whenever I need to address to a stranger, I use «Прошу прощения, ...» or «Извините, ...». There is no actual need of personal addressing. No misters or товарищи.