Hello. As an Indian national living in France, do I need a visa for Hong Kong and mainland China?

How long will you stay in HK? If the staying time is less than 14 days, you can only use your valid passport to travel. If you stay longer, you need to apply a permit in advance.

For mainland China, you need to apply a single entry Tourist L in advance. Since you live in France, you can try to apply for it in France with your resident permit in France, valid passport, an application form, a recent taken photo, your round trip tickets to China, hotel bookings, your income statement in France, your issurance in China.