Did divorce occur in the three cases mentioned, which are: the husband's saying "you are not under my responsibility" then taking her back, his saying to the wife's sister "your sister is divorced" then taking her back, and his saying "if you leave the apartment door without my permission, then you are divorced" then setting the oath's duration to 24 hours and her leaving after this period?

Divorce occurs for the first and second times. As for the third time, if the husband made divorce contingent on his wife leaving without his permission, and then said he would make this for only 24 hours, then it appears that this implies his permission for her to leave whenever she wishes. Thus, the oath is dissolved, and divorce does not occur if she leaves thereafter. This is based on the statement in "Zad al-Mustaqni‘": "Not if he permits it whenever she wishes," and Sheikh Ibn ‘Uthaymeen’s explanation of it, which states that permission for her to leave whenever she wishes dissolves the oath.