1. I wouldn't say there's an exact time. During the night, just before dawn, through the early dawn, when the sky is getting lighter, maybe just before the sun rises. 2. I think I've only heard it as "in the wee hours of the morning" 3. Early this morning, in the early morning, etc.

It is used here in the US too, perhaps because of all the Scottish and Irish immigrants. The phrase refers to the hours after midnight, and probably before dawn. It is a colloquialism, so it might sound funny coming from a foreign speaker. "Early in the morning" or "Very early in the morning" might be a better choice.

1) I would say up to 5 a.m. would be seen as the wee hours 2) In the wee hours of this morning 3) I've only ever heard this used by people from Scotland, I could be mistaken. The more common thing would be to say "the early hours"

I got it. Thank you so much again!

Instead of 'wee hours' you also might hear 'small hours' used. It is the same idea ('wee' is another way of saying 'small') but avoids the regional colloquialism.