question.
3）女基督徒去海滩是不是必须穿全包裹式的游泳衣（中东式），男基督徒呢 ？

男 女 including 基督徒 去海滩 or any other places 必须
穿 衣 that serves primarily to cover human beings SHAME
after fallen, as a self-measuring, 穿 衣 should make him
or her feel no SHAME.

During Lin YuTang's time, he found girls in college had less
SENSE OF SHAME than girls in Ba1 Da4 Hu2 Tong, therefore,
they chose clothing accordingly.

In short:
one can do anything he/she wants with consequence,
but
nothing had better not be viewed over-spiritually and over-politically.