What is wrong in "Please don't pluck the flowers" and other phrases used in the Indian subcontinent?

In the Indian subcontinent, especially India, there are many English words or phrases which are not a part of dictionary or not used in other parts of the world.

The first one is "Please don't pluck the flowers". I might not be proper, but I don't see anything wrong with this. It is pretty easy to understand what the person is trying to convey.

The second phrase is "Please do the needful". This is said to have its root in improper translation from an Indic language. Even though it might sound weird to non-Indians, it is a very simple way of saying "Please do what we expect you to do in this situation without being provided a detailed explanation".

In Indian English it is very well understood when someone asks "I have a doubt in this concept". In UK, doubt is taken in the context of "suspect", but in India, it is taken as "having a problem or not being clear".

There is another term which is actually not in any dictionary — "prepone" which is used as an antonym of "postpone". Even though it does not make sense, its meaning is pretty much straightforward.

After giving this long explanation, here are my three questions:

• What is wrong in "Please don't pluck the flowers"?
• What is wrong with "Please do the needful"?
• Isn't it acceptable to use words like "prepone" even though it not in the dictionary? It is pretty much well understood (especially by people who scorn at others using this word)?

Update

I would like to explain when and where these terms are used:

• "Please don't pluck the flowers" is used very rarely, and it is pretty much rare to hear this
• "Please do the needful" is used mostly in corporate environments by a person to their subordinates. For example, a project manager gets a mail from marketing or quality assurance about something missing or incomplete, then he/she sends a mail to the subordinate with the body "Please do the needful". The subordinate is usually more well-versed with the work which has to be done. It might be his/her expertise so the manager might not tell what exactly needs to be done as is left upon him/her to figure out.
• "Prepone" is used only in one context — opposite of "postpone" the event. The most common usage is "This event or meeting has been preponed".

Solution 1:

Regarding "do the needful", Wikipedia has an article on the subject. It indicates that it was more common in English in the past. I don't think it is grammatically wrong; it is just more a matter of idiom in US/UK English. There we would more likely say "do what is necessary" or "do whatever it takes".

The same is true with pluck the flowers. It is grammatically fine; it is just not the idiom.

In regards to prepone, this is an Indian coining, and I personally think it is a great word. However, it has not made its way to Europe and the US. Frankly, I think it is our loss.

Indian English is a perfectly legitimate dialect of English and need in no way feel inferior to the mother country's version. On the contrary, India has been an abundant supplier of words and phrases to British English, and we owe the Indians a debt of gratitude in that respect. "Pluck the flowers" might be a little odd sounding to the British or American ear, but Americans "could care less", while Brits "couldn't care less", and Americans don't get too pissed, and Brits don't get too pissed off at each other about the differences.

As we English speakers like to say: vive la différence.

Solution 2:

The other answers here are generally good and correct analyses of the history of these particular phrases. I just wanted to underline that there isn't anything wrong per se with these phrases; they are just not idiomatic in American and British English. They are not things that native speakers of American and British English would say, so if you say them in the U.S. or Britain, your speech marks you as a foreigner. If you are trying to master either British or American English, then part of that mastery would be understanding not to use phrases like "please do the needful" and "please don't pluck the flowers" and the word "prepone".

As a side note, I personally don't like the phrase "please do the needful" very much. I find it a little too condescending and dictatorial for my tastes, as though the details of what is necessary are too trivial for the speaker to even know what they are.