Were we forbidden from placing one foot over the other while sitting or sleeping with them extended, and from sitting and leaning back on the hands, because it resembles the posture of those who are tormented?

The Prophet, peace and blessings be upon him, forbade a man from raising one leg over the other while lying on his back. Scholars have interpreted this prohibition to apply if it leads to the exposure of the 'awrah (private parts). Similarly, some postures of reclining and sitting are forbidden, such as placing the left hand behind the back and leaning on it, or leaning on the left hand during prayer, because these are postures adopted by those who are being tortured. As for sleeping with the feet extended or with one foot placed over the other, there is no prohibition in that, as this is a natural way of sleeping, and the pen is lifted from the sleeper (meaning they are not held accountable for their actions in that state).