Does skin that has peeled from the lips constitute a barrier that prevents water from reaching [the skin] during the obligatory ritual bath (ghusl), which could invalidate the ghusl, prayer, and fasting?

The presence of skin on the lip does not affect the fast; it remains valid in all circumstances. The invalidity of the ghusl (definition) (ritual bath) for janabah (definition) (ritual impurity) does not affect it, as the Prophet, peace and blessings be upon him, would be overtaken by dawn while in a state of janabah, then he would perform ghusl and fast. Regarding ghusl, skin that is attached to the body is not considered a barrier. However, if it detaches and its removal causes no harm, then what is beneath it must be washed. If the aforementioned skin was attached during ghusl and only detached afterwards, then the ghusl is valid. But if it detached from the lip during ghusl, then its place must be washed, knowing that the water reaching the limb is sufficient, and ghusl does not require rubbing, according to the majority of scholars.