Exactly there are no rules followed strictly in the corporate world except for cutting down your salaries by giving reasons like not reaching on time or sandwich holiday and what not. And one of the reason why Indians don't hesitate to take multiple breaks.
There is nothing difficult for the corporate, A didn't completed their given task on time so no compensation even if A would have started by day 1.
Let's continue your example itself, if A finishes all his 5 Assignments at the given time, i.e. Friday but the manager suddenly comes and tells A to extend some time on Friday as the client request 1 more assignment, but now it's not A's duty as his 5 Assignments are done on the given deadline and now he has to extend because the manager asks him to do another at the last minute so A extends and he will be rightful to ask compensation and at this point the corporate has to give if they are following the rules.