1. It depends on the occasion. If it is a big hotel, you'd better wear formal clothes. After all, if it is a hotel wedding, it must not be too rude. Do China people care about face? If you don't have formal clothes, you can also wear some casual suits, skirts and dresses (just my suggestion). If it's just an ordinary small hotel, you can be casual, but you must be clean and tidy.

Let's see if people have any taboos, such as not wearing white clothes. Maybe not now. After all, there are so many people wearing wedding dresses, but those with old people at home may be a little disliked.

Your own age, but you should be an adult here, so you should dress neatly.

I hope my answer can help you.