Is it from the Sunnah to delay washing the feet in wudu until the end of ghusl, or is the Sunnah to complete wudu fully first? And if one delays washing the feet in a recommended ghusl, is this considered wudu, or does it interrupt it?

It is recommended to begin the ritual bath (ghusl) with ablution (wudu). It is permissible to wash the feet during the ablution or to delay washing them until the end of the ghusl. It is preferable to wash them during the ablution unless there is an excuse, such as the bathing area being muddy, in which case their washing is delayed. Both methods are authentically reported from the Messenger of Allah, peace and blessings be upon him, and the ablution of one who delays washing the feet is valid and is not considered a中断 of the ablution.