You're new in town, right?
My sincere advice would be to forget it. Legally, everything depends on the contract but enforcing a contract is troublesome - even if you win in Hong Kong Small Claims Court.
If you want to go down the legal route it will cost you a lot of time, money and effort. And for what? Air conditioning cleaning cost and lock changing? Put your effort into making money in your job, save up and eventually get a place of your own.
I am a former landlord and I used to pay for reasonable replacement costs - such as fridge and aircons that broke - plus cleaning every couple of years or so. However, I was trying to keep my tenants on side.
Many HK landlords don't care and -- in their defence -- if you give into to too many requests, many tenants start treating you like hotel staff. It basically boils down to a reasonable balance which is why I wouldn't be over confrontational.