Is the Tawwarruk posture obligatory for women in prayer? And is it incorrect for her to sit on her knees and the front of her shins? And is it correct for some women to sit on both buttocks with the left thigh, placing both legs on the ground from the right side?

Iftirash (sitting on the left heel with the right foot upright) and tawarruk (sitting on the left thigh with both feet extended to the right side) are not conditions for the validity of prayer. Rather, it is permissible to sit in any posture, especially out of necessity. Men and women are equal in this regard. The sunnah posture of sitting is recommended, not a condition, so the prayer of one who does not adopt it is valid.