Learn English – “has been opened ” or “being opened”

To me, the first choice sounds more natural. It emphasizes the nature of writing to someone as an intermittent action. The second, as FumbleFingers noted, seems to emphasize that the speaker has been in the habit of writing to the person in question.

Either one implies that the speaker should have been expected to write to the person referenced. The second, though, implies that the expectation is based on past experience, i.e. previously the speaker was in the habit of writing to them. With the first, all we can conclude is that there is a social expectation (thus both the apology and the implied definition of "a while."

Your understanding of the three phrases is not quite correct:

1. has gone to - there or on his way to;
2. has been to - someone has been there but he is on his way back; OR someone has been there at some point in the past and is now elsewhere
3. has been in - someone is still there; someone has gone there at some point in the past and is still there

So these statements:

1. Have you ever been to / in Greece? - Yes, it's a very beautiful country;
2. When did you last go to Canada? - I've never been to Canada.

You could say HAVE you ever gone to Greece and it would be correct

I have never gone to Canada is also correct I have never been in Canada, while it would be understood, might sound odd to some. In this sentence I have never been TO Canada, would be correct.