1. Many shops and private shops in Hong Kong can basically accept RMB payment, but the exchange rate is relatively high. I suggest you change it into Hong Kong dollars and spend it in Hong Kong.

You can basically pay by credit card in shops and hotels. One thing you should pay attention to is that debit cards or single-currency credit cards are UnionPay cards, and you can directly use UnionPay's network. When you swipe your card, you can directly convert it into RMB according to the foreign exchange rate published by the People's Bank of China on the day you swipe your card. If you use a dual-currency card, you should also use the network of UnionPay (don't use the network of VISA or MasterCard), which can save the exchange cost. When you return to the mainland, you will also use the foreign exchange rate on the repayment date.