Learn English – Usage of the word “latest”

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

Evidence from dictionaries:

Hence, when applied to time, is defined as:

2. from this time; from now: They will leave a month hence.

There is not a shred of evidence in any dictionary or in common/traditional/standard usage that hence can be used to refer to the past. So, as it is unsanctioned by any important authorities, and unused, I would say this is a case of either misconception or mistake on the writer's part.

In the quote, ago is the proper word to replace hence with. It is possible that the writer confused hence with since, as since is sometimes used as a synonym of ago.