* An answer from PMP4Sure mentioned that lessons learned will include how certain groups/persons caused failures and delays inside their own organisation.Is this correct?

Yes, so why when the project is suspend by sponser of some reason, it is still need close the project and update OPA.
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* Some options asking for the appropriate TT had correct answers which were named differently from that in PMBOK.For the real exam is it possible to eliminate an option if its a term not found in PMBOK?
For Eg.Settled Negotiations instead of Procurement Negotiations

No idea,but I suggest you have you identify that is make-up terms or different name First.
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* Does the exam ask complex calculations on NPV,ROI??(like those found in Oliver Lehmann)

As my LL, NPV = yes, ROI=no

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* Answers to scenario-based questions also tend to have different answers.For eg.A question rearding a team comprimising of members in different geographical locations having conflicts.One answer is promoting more number of informal communications and other is Colocation.I found the colocation answer strange.

Colocation maybe wrong, Colocation mean team members in "one place", virtual team can't be.
Where is this question from?

Correct me if i am wrong.

If the question is straight forward on ITTO, then you can eliminate the terms which are not found in PMBoK 5. However dont depend on elimination to answer correctly. Try to understand the ITTO.

As for your question on Co-location, when the members are in same location , the human aspect comes into play and the conflicts reduce due to people seeing and knowing each other. Over the phone or Video conference its common to mis-understand the other person. Even if you promote Informal communication, there is a limit to how much people will communicate when the are not in same location.

I teach an exam prep course so I feel pretty comfortable in sharing the following with you. My first suggestion is to be certain that you are using only materials/sources that are clearly based on the PMBOK 5th Edition.
*Yes, one requisite knowledge area of the exam is Stakeholder Management. Anyone impacting or impacted by the project should be considered a stakeholder so it stands to reason that internal stakeholders could cause failures/delays. Check the definition in the PMBOK (5th Edition) glossary for more clarification.
* Use caution regarding Settled Negotiations/Procurement Negotiations for several reasons. Without a lot of detail, the PMBOK 4th Edition used the term 'Negotiated Settlements.' The 5th Edition uses 'Procurement Negotiations' at both the beginning and end of a contract (now called an agreement.
* Yes! You'll see a number of possible formulae on the exam. There's a great app called Formulas PMP that will help you.
* There will be MANY scenario-based questions on the exam. There are some great tips for answering those but that is beyond the scope of your question. I believe 'Colocation' is correct in this context as the question specifically noted different geographic locations. Unless there is information I'm missing, they probably wanted you to ID the TT Colocation.

As mentioned I teach a related course. If you want more details, you can message me. You should also check out http://www.pmstudy.com/PMP-Exam-Resources/free-mobile-apps.asp. The apps are for both Apple/Android. There are other free resources and I guarantee all these concepts are covered in the classroom course.

Best of luck!