$1.$ How to examine the correctness of the functionality

$2.$ Level of specification and where these levels are supposed to be processed

$3.$ Why we need measurement? And how the measurement is planned and executed

$4.$ Differentiate system modelling from system behaviour modelling?

$5.$ How we model the behaviour?

How model the behaviour from the quality assurance perspective is to be divided into $2$ part? The $2$ indicators we need to deploy in the workflow scenario

Please explain all these questions with every detail $!($details are important please do not skip$)$