About questions like: "What is your greatest strengths and weaknesses?" How to response?Are employers really candidly assessing your biggest flaw?

Never share your weaknesses in answer of this question. Always use a minor strength as an answer to weakness. For example: Perfectionism in work, Reviewing more often etc etc 

just relax and answer in flexible words

my great strength  :  make a good plan for how I work and  how I handle my tasks in Effective and efficient way

my Weakness :  I want to work and get perfect result   , and actually you have to finish in just good way donot waste your  time thinking  in Improvements or future  at the moment 

and after that you can improve ,, you will learn every minute till you die  

Sometimes, your interviews goes excellent throughout the process but answering about your weakness can ruin your all interview. However, my suggestion is not to tell your "Professional Weakness"  nobody is perfect, everyone has flaws, so, we make all possible efforts to improve ourselves. This is not cheating with the interviewer but gaining a chance to improve.

Lets say you mentioned your weaknesses as follows.

1. I am weak in MS Office.

2. i get upset when i am not meeting the target

3. sometimes i get angry when my subordinates dont obey me.

4. i am not pressure handler.

these kinds of weaknesses can make your chance of selection very weaker.

Lets try turning your weaknesses into strengthens.

1. i go to bed early.

2. i am keen on details.

3. people say i am skinflint, but i dont think so.

Regarding your Strengthens, keep it broader.

1. I am flexible, wise worker, sincere and polite.

Some Accept it and another no

its dependent what he effect of our weakness

my strength is im a hard working ,self motivating person,i eager to learn new things,im optimistic ,goog reasoning,a confident one.my weaknesses are,i easily trust and help every one ,i feel worst  when i talk about my weaknesses,i torture myself if i had a trouble...

it depends on that what situation is going on

Assessing your strenghts and weaknesses is not about knowing your greatest flaws if we view it positively. Your answers regarding your weaknesses and strenghts can help the recruiter or employer determine which areas they can maximize your potential that is beneficial to the employers business requirements. Your areas of strengths is what the employer's immediate need to hire you; while your weaknesses can be dealt with as you progress with your job requirement.