Is it necessary to perform all the Sunnah acts of ablution if a Muslim performs only some of them, and does ablution become void by omitting some of the Sunnah acts after performing others?

First: Wudu' (ablution) with all its Sunnah (prophetic traditions) and mustahabbat (recommended acts). And if the one performing wudu' limits himself to the Fara'id (obligatory acts) or adds some Sunnah acts but not others, his wudu' is valid, but he misses out on a great good.