1. Do anyone whom was working before for the HO or have Insider information which could solve the one million pounds question about how the OP operate the BC , what kind of papers, documents , information they mainly looking for that will help take the decision about 80% of cases in short time and all this 80% is successful, what kind of internal/external checks they do in order to decide upon a case, like the UKBA, HRMC, Councils ....etc
Do anyone have real hand on experience about this fatal point ?
They Work as per the guidelines issued. One set of guidelines is issued for the OP. Another set of detailed internal instructions is issued for case workers.
For Instance the list of supporting documents is there in the Form AN.
Now based on what you actually furnish they will use their discretion to judge.
Individual cases and circumstances vary. So having a standard procedure is not realistically possible. This is where each case
workers judgement comes into play.
When they take a wrong decision , the OP goes for an administrative review in which case for an additional 80Quid your case gets a relook.
Immigration decisions are final and cannot be appealed.
2. Do the more documents I provide will help, or sometimes more documents mean more checks and could have delayed, for examples do I have to provide all air tickets in/out of the UK , all 3 years bank statements & utilities bills or just the last year will be enough, family information like birth certificates, school letters , NHS letters ..etc do this extra docs help or not
from my small experience from the ILR face-to-face meeting , they just use a very few documents to get the decision and they told me why you bring all this , most of them is not needed or the OP by mail is different and it's completely another story.
Provide relevant documents to bolster your case and convince a decision in your favor. Stick to approved list of documentary supports and add only those additional supports like the SAR where your old passport was lost and the pages of have gone missing (Just for your mental peace).
The logic more the merrier does not work. So if a person provides double the documents you provide , will they give a free naturalisation to one more person of your choice? LIKE BUY ONE GET ONE FREE!!! I guess not! 
3. Why most of the immigration advisers provide conflicts advice, some one told me do this and the other do another advice which is totally different, the forum here help a lot but many inputs are not complete
With due respect Immigration advisers have to earn a living. Like the 5 fingers of your hand each comes from a different background, different experience level, different mindset and approach towards his/her profession.
Also generally migrants tend to ask the same question more than once and in different ways to different people and get different responses based on the perception of the person responding to their query. In their anxiety bit part info is furnished many a time. So the blame cannot be fixed solely on immigration advisors, if it makes sense.
As far as this forum goes, its a service where people share their experience to help others reduce their anxieties and get an overview or basic guidance on how to go about their individual cases. The people who advise on a web forum are neither privy to actual circumstances of the OP nor do they have any pecuniary or vested interest in giving the advise.
As with any other web forums people of different mindsets, with different objectives visit here and hence you see a variance in responses, unwanted interjections which add to the confusion. It is upto you to take a decision based on your personal perception and discretion. You should thank your stars for the service and free valuable inputs you get. Many of us who entered UK much earlier did not have this luxury.
If yours is a complicated case or you are very anxious to the extent that your blood vessels are going to burst, you should immediately take Metformin and consult a doctor. Once done you should get hold of professional legal advise.
Hope this rests your anxieties!!
