1. the Ocean Park is open, but the dolphins and sea lions at Ocean Theater will take a short break until to Jan 29.
2. it is reported that there will a few light rain on Jan 12, as well as the other days are mainly cloudy. The temperature is around 15C. So, a thin sweater and jacket is ok.
3. The cost of food will depend on what you would like to have. Generally, HKD100 is enough for budget B L S.
4. for these must, I think you could refer to other's travel plans below, or the introduction on this page:https://www.travelchinaguide.com/attraction/hongkong/

ok.. thank you so much ms Sisley.. :)

Speaking to your questions on costs:

1. Food - as Sisley mentions, this largely depends on what you wish to eat. Local places (roast shops/noodle shops) will cost you anywhere from HK15-40/person per meal; Western casual restaurants will run HK50-150/person for lunch and HK100-250 for dinner. If you're planning to dine in Lan Kwai Fong, SoHo, or Wan Chai (among other top entertainment areas) the Hong Kong Card would save you 50% off. It's available at nearly 100 restaurants and spas - see www.thehongkongcard.com

2. Hotels vary quite a bit. An excellent choice is The Fleming in Wan Chai (www.thefleming.com.hk). It's a nice 4-star boutique hotel and is currently offering rates of HK800/night. It's difficult to find anything under HK500, though sometimes the Butterfly hotels in Wan Chai and TST (www.butterflyhk.com) have some good promotions.