Can a Master student's thesis be kept indefinitely until the advisors have extracted everything the student has to give? Is it legal for advisors in the US to prevent a student from graduating by "suddenly, about a week before deadline, realizing that what the student was doing for the past few semesters is not what the advisors asked for and the student has to redo the project design all over..." . I understand that the advisors might not be satisfied but shouldn't they notice this months ago?

Also, even after graduation, how much long are they, legally, allowed to ask for changes and feedback? Is it normal for professors to threaten the student pre but also post-graduation that they will take actions if the student doesn't do as asked?

I can elaborate if any questions arise but the main issue is that since they are occupied with their own issues (both professional, personal AND a mix of "personal aspirations" agenda interfering with the professional time they are paid to have with their students) and pay no attention to what I'm doing (while I constantly chase them to show them updates but they refuse even to look at my work, they literally closed my laptop's lid one day).
This is not strictly speaking a legal issue. There are generally internal university regulations that govern theses and dissertations, but enforcing them is not something that can be compelled through force of law.

There is normally a limit on the amount of time that can elapse for changes to be demanded, but this is entirely institution-dependent. Usually, though, any such period coincides with the conferral of the degree. At that point, the advisor and committee cannot ask for more changes.

All of that said, someone has committed derilection of duty in advising you. If there was a question about whether or not you were ready to defend, it should have been addressed before you wrote up the entire thesis and scheduled the defense. (It may have been the responsibility of a thesis committee, not the advisor, to make this decision. I don’t know without knowing more about the departmental regulations.)

Right now, I would talk to the other members of the committee, the chair of the graduate studies committee, and the chair of the department to figure out what can be done. This is not a good situation, and if your defense is scheduled for the near future, you may need to postpone it at least temporarily to avoid problems if your advisor is deadset on you redoing everything.