Is anal sex considered an act of disbelief (kufr) that expels one from the fold of Islam? And is performing ghusl (ritual bath) after it, similar to ghusl for janabah (major ritual impurity), sufficient for prayers to be valid thereafter? And is a non-married woman required to observe an 'iddah (waiting period) after sincere repentance from this act, knowing that it does not cause pregnancy?

Anal intercourse with a foreign woman is zina (fornication/adultery) that necessitates the Hadd punishment. It is a graver sin than anal intercourse with one's wife, though both are forbidden in Islamic law. This act is considered a minor disbelief (kufr asghar), and its perpetrator does not exit the fold of Islam unless he deems the act permissible, in which case it becomes major disbelief (kufr akbar). One who commits this sin must offer sincere repentance (tawbah nasuh), conceal the act, and not inform anyone about it. Anal intercourse necessitates the iddah (waiting period), but a single menstrual cycle for istibra' (clearing the womb) suffices. It also necessitates ghusl (ritual bath) for both the perpetrator and the one upon whom the act is perpetrated.