"good age", used in pointing out that someone is doing something below their age group

not necessary to; don't have to

If only ~

It's good / okay to... / is fine

a surname

酸い: sour (taste)

水: one of the five classical elements in traditional Chinese philosophy and medicine: see the "Wu Xing" entry on Wikipedia / 粋: chic, style, purity, essence

水: Wednesday

水曜: Wednesday / 垂楊: weeping willow

素直: tractable; honest, direct