"used to with interval" and "around vs about"

[Tsy]

1. I used to work at Company A for around/about 2 months
2. I had worked at Company A for for around/about 2 months

My first question is that if a past perfect clause could come alone without a past simple one.

When talking about time, I think the word about can be followed by both of interval and a point of time" and around can be followed by only "a point of time".

Like "Plase come to meet me at around 6 AM."
A: What time is it ?
B: It's about 10PM.

Is this correct ?

How do we know which one between around and about is more suitably used ?
Is there a case that the word around and about can be used interchangeably ?

Thank you in advance.

[Tsy]

I forgot to ask about one thing that if "used to" can be followed by an interval.

I also found a page that is related to my question.
http://rightwords.co.nz/index.php?option=com_content&task=view&id=51&Itemid=30

[Barb_D]

Better is "I worked there for about 2 months" or "I worked there for around 2 months." You can use either "about" or "around."

If you use "used to" then don't put the time with it. "I used to work there." Or "I used to work there for a couple months every summer" to show repeated action.

It's just fine to say "It's about 10 p.m."