grammaticality - Using the word 'Only'

I am confused about using the word only. I often hear it being used in many contexts that sound wrong to me - but I'm not sure if it's me or them.

Let me give some examples:

A: Where were you yesterday evening?
B: I was at the coffee house.
A: Hey, I was there only; how come we didn't meet?

I guess the correct usage here would be I was also there or I was there too, right?

How about this:

A: Did you complete that task?
B: No, but I am doing that only

The word only is used here to stress on the fact that he is doing that (and not something else). I guess this usage stems from an equivalent usage in Hindi and other Indian languages. What's the correct way to express this? I feel I am still working on that is not the same - it sounds more like I haven't figured out how to do it, as opposed to this is a difficult task, it'll take some time

Another one:

A: How many questions have you asked in this forum?
B: I have asked only one question.
C: I have asked one question only.

Who is correct - B or C?
I'm with B on this one, but I don't know if C is correct too.

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PS: In case you haven't guessed it already, I'm not a native English speaker :)

Answer

Example 1
seems to be legitimate Indian English, see

Something which Indian English has

that is not found in other varieties
of English is the use of only and
itself to emphasize time and place. It
comes from the Hindi word hi and
produces sentences like "I was in
Toledo only" and "Can we meet tomorrow
itself?"

extract from language in India

More discussion on 'only' in Indian English here Dustin Freeman

Example 2 is probably Indian English too. You could say you are concentrating on that task, if you wanted to be better understood by a foreign audience.

Example 3: either is correct, I would think the 2nd is more colloquial

I don't think you be misunderstood with any of these colloquialisms. To me they are colourful additions to the language