Kindly tell me, which outline for essay is more preferable?
A detailed and lengthy or simple one, two word outline?

I would certainly prefer a concise and brief outline over the lengthy and jumbled one. There were some posts in a thread in which some serving CSP officers (I think including Redmax) revealed that their outline was brief and to the point. http://www.cssforum.com.pk/css-compu...-passed-2.html

One can extend various reasons as to why brief and concise outline is better than a extensive one. Firstly, just by glancing through the lengthy outline, examiner gets an impression of what the entire content of essay will be. On the contrary, a brief outline (that does include all important points) may arouse a compulsion in the mind of examiner to go through the entire essay to judge the content. Hence, sometimes brief outlines may force the examiner to read the entire essay and subsequently by virtue of ‘some’ relevant points, candidate might obtain the passing marks.

Secondly, a lengthy outline is difficult to draft and formulate as the flow of information should be sequential and it might take some additional time to articulate a lengthy outline. Moreover, sometimes as one starts writing the essay, some novel, new or forgotten points tend to originate in the mind. A brief outline can tackle such minor additions but a lengthy and detailed one fails to do so (unless to leave enough space for some points).

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The one who is most deserving of thanks and praise from people is Allah

Ok. Thanks alot.
What about the bulleting? Is it necessary that the main heading should be in Romans while sub headings alphabetically?

Sorry, I have no idea about this sort of requirement. However, it is always better to write sub headings in alphabets in contrast to the main headings which should be denominated in roman numerals. I would follow this strategy to effectively differentiate between levels of headings.

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The one who is most deserving of thanks and praise from people is Allah