SHORT ANSWER:
Yes, the continuative present perfect may be used to signify a state which continues right up to the present regardless of whether it continues in the present. It is not, however, used to signify a state which does not continue right up to the present.
LONG ANSWER:
The 'continuative' present perfect establishes the past event or events it names as a state which endures right up to the present.
Situations grammatically depicted as states are presumed to continue indefinitely, until something happens to end them.
Consequently, the present perfect permits you to infer that the state it describes continues in the present. In fact, this is the default assumption with an unqualified present perfect. If you had only the statement “I've been driving a hearse for the last 25 years” you would legitimately infer that he is still driving a hearse.
But the present perfect does not entail—logically require—the continuation. Linguists call this an implicature, as opposed to an implication: it is in inference which may be cancelled by a contrary fact. That's what you have here, with the statement “Today is my first day driving a cab.”
Note, by the way, that there is in this particular use of the perfect, no difference between the use with the progressive, “I have been driving”, and without it, “I have driven”. The phrase “for the last 25 years” imposes the same continuative reading on both.
Note, too, that because the hearse-driving does not continue into the present the speaker might with propriety have employed the ‘simple past’: “I drove a hearse for 25 years.” I suspect he uses the perfect (and the progressive) because what he wants to convey is that there is a continuity in his activity: “I’m still driving, what’s changed is that now I’m driving a cab.”
Note, finally, that the notion of ‘present’ is defined pragmatically. Obviously when someone says he has driven a hearse for 25 years he does not mean that he drove continuously throughout that period. By the same token, the ‘present’ which that driving continued ‘right up to’ is not the moment in time when the statement is uttered but “today”
The case of John’s tardiness is a little different. In the circumstances you describe, neither the continuative present perfect nor the phrase “for the last 30 minutes” is proper. You are dealing with a much different timeframe and scale than the cabdriver. Your answer (“alas”) makes it clear that you are pragmatically defining three distinct epochs: 1) you wait for 30 minutes 2) you depart, and a couple of minutes elapse—long enough, at any rate, that you are no longer in the vicinity of the appointed meetingplace 3) then John calls. Consequently, the state of waiting (1) did not continue “right up to” the present (3).
Here are some ways you might express the facts:
I waited for you for thirty minutes, but, alas, when you didn’t show up I left.
I waited for you for thirty minutes, but, alas, I’ve left now.
I waited for you for thirty minutes, but, alas, I had to leave.
You should not employ the progressive I was waiting here; that is employed to speak about something which happened while you were waiting.
Tricky question. I liked it.
It can happen bothways.
Opinion 1:
I consider that the pictures belong to some story/event. Storytelling is always in past because the event has happened. However, in some sentences, present tense may be used but that will be special cases. Overall, it'll be in past.
I quickly referred my daughter's text books and found that most of the questions are in past tense. Having said this, it'll be answered in past as well.
The pictures are just for the purpose of illustration and will make kids/the readers understand the scene/scenario and not the tense.
Opinion 2:
You may use the present tense if you are talking about that picture and asking it right now. The way 'find the differences between two pictures comes in newspapers and magazines'. If there's one single picture and it's not a story, you may put a present tense. That's because these questions are based on the picture and not the story. The picture is right in front of you and you are asking questions. The moment, the picture becomes a part of story, and is a kind of lesson you find in text book, it takes past tense to narrate, ask and answer.
Best Answer
I agree with those in the comments, that using "What [were you]/[have you been] doing?" is much more likely to be interpreted by the recipient as rude, or at least intrusive. I can't think of a situation in which I would use either of these phrases unless I was essentially accusing someone of doing something they shouldn't have been.
If I'm interested in what someone has been doing, instead of saying "What were you doing last week?", I might say "What did you get up to last week?", although if the last time I spoke to them was much more than a week ago and there's no specific reason why last week was important, then I'd probably just say "What have you been up to?".
Disclaimer: I'm a native UK English speaker, so some of the above might be a little regional to the UK. I have spent a fair bit of time in the US and understand a decent amount of their regional variations, but I'll let a native US English speaker fill in the gaps if necessary.