[Answered ]-Django form with Dynamic fields. Invalid but no errors

Finally, the problem is solved.
This happens because the form is unbound, because of one of my careless mistakes:

form = Review_Form(sentences=sents)

instead of what it should be:

form = Review_Form(request.POST, sentences=sents)

I answered this because I think this is probably useful for other new developers like me.
Read more on unbound and bound forms, if you like, from here: Django form API