Is it permissible, if yellowness appears after ghusl, to adopt the view of Ibn Uthaymeen that it is not considered menstruation? Is it impure, and does it necessitate changing clothes and performing ablution for every prayer? Is the duration of menstruation considered to extend until the yellowness ceases, or does it end solely with the cessation of blood? And is it obligatory to re-perform ghusl and make up missed prayers if yellowness appears after ghusl, knowing that the bleeding had stopped before that?

Yellowish and brownish discharges are considered menstruation if they are connected to blood. However, if they appear after seeing the sign of purity (by dryness or the white discharge), they are not considered menstruation.

The two scenarios mentioned in the question are not considered menstruation, as yellowish and brownish discharges are only considered menstruation if they are connected to blood. There is another opinion among some scholars, including Sheikh al-Islam Ibn Taymiyyah and Sheikh Ibn Uthaymeen, who hold that yellowish and brownish discharges are not menstruation in any case. A layperson should follow the opinion of a scholar whom they trust.

If the yellowish discharge is not menstruation and its flow is continuous, then it falls under the ruling of perpetual impurity, meaning it is impure. One must perform istinja (definition)' (cleansing oneself) from it, take precautions (such as wearing a pad), and perform ablution for every prayer, just as a woman with prolonged vaginal bleeding (mustahadah) does.