Looks like OP is relying on google translate which isn't accurate all the time and could cause even more confusion. If anyone speaks the language, check out OP's thread in their local board:
新人求助,库币卡充值应该怎么办?From what I understood, OP's deposit didn't show up in their kucoin wallet hence why they reached out to kucoin's support and was asked some personal info/documents.
I'm not sure if this would translate well but it looks like the deposit has triggered kucoin's precautionary measures which is why OP was asked for such info. For now, follow the support's instructions to get your money back @OP, and if you feel like they are asking too much info about you, consider if it's worth the amount locked.
You can start worrying about them pocketing (or holding hostage) your money when:
1. You have complied to everything and there's still nothing.
2. The whole thing has been taking too long
3. They keep asking either for the same thing or more and more documents.
Hacking/bankruptcy would be very unlikely basing from your case.