Is it obligatory to repeat ablution for one who unintentionally erred in its order, and is order a condition for ablution? And what is the correct order in light of the Sunnah?

The Shafi'is and Hanbalis held the view that sequential order (tartib) is obligatory in ablution (wudu'), citing as evidence the noble verse: "O you who have believed, when you rise to [perform] prayer, wash your faces and your forearms to the elbows and wipe over your heads and wash your feet to the ankles," and also the actions of the Prophet, peace be upon him. Conversely, the Hanafis and Malikis held that it is a Sunnah (recommended), arguing that the conjunction "wa" (and) does not necessitate sequential order, and also citing the saying of Ibn Mas'ud, may Allah be pleased with him. The matter is one of scholarly disagreement (khilaf). For whoever is convinced of the obligation of sequential order, he is required to repeat his ablution if he did not observe the order, whether intentionally, by mistake, or out of forgetfulness.