Benefits when transferring from Australia to China

I work for a good rich company.
Before I see my transfer offer from Australia to China; I was interested in what some of the differences in benefits between the 2 countries might be?
Australia: 4 weeks leave and around 12 public holidays.
Sick days: I am assuming I loose my accrued sick days. Do you get sick days in China, or are you not allowed to get sick?
Do you get paid superannuation in China? Once I leave China in 2-3 years can I extract that money?
Salary: Can I easily transfer more than $50k USD annually back to Australia to pay my home loan off? What is the most cost effective way to transfer this money to get the best rate?
Shares: I have shares that have not yet vested. What would happen to them?

What else have i missed?

I have read that some companies may offer 2 annual flights back to Australia. Not sure if mine will do that.

They might just pay me a relo package, I would prefer the cash and move a minimal amount.

Thanks for any advice. If you can think of anything I should try to add to my negotiation please advise. Can I ask for a guaranteed job back in Australia after 2-3 years, written into my contract? How would that work? Kind of like an assignment for 2-3 years?

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