非基督徒及非天主教徒可否在教堂行禮？

可以,只要你找到一神父是不介意你的身份是否教徙就可以了
我是從不知那裡看來的,好像是某神父說的
你的婚禮有否伴娘及伴郎就自己決定吧

如果為了行教堂而入教就無謂了

伴娘及伴郎是個人問題

Mostly cannot. But, I've heard once a pair of famous people got married in a church though they are not christian or others.

咁係咪唔使伴娘及伴郎？ not really, some people use them even they are not getting marry in a church. May be for taking photo or for the banquet at night.