PR chances: Singapore father, M'sian Chinese mother, Brit kids

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I'm a Singaporean citizen that is likely to be moving back with my family in about 7-8 months time. My current employer will be relocating me from back to Singapore.

I'd like to get thoughts on my family's chances of getting PR with me as the sponsor.

My wife is Malaysian Chinese, and I've got 2 young daughters who were born in the UK and are British citizens (neither Singaporean nor Malaysian). Our profile:
- My expected annual salary S$200k+
- My wife has a postgraduate degree from the UK, but will be a stay-at-home-mum
- We've been married 7 years, marriage registered in Singapore
- We are in the 35-40 age band

We are still overseas at the moment:
- Is it possible to apply for PR whilst still overseas, i.e. a few months before physically moving back to Singapore?
- Is there a minimum residency requirement to be satisfied either (1) at the point of application, or (2) at the time the PR is approved?
- How long do PR applications of this sort normally take?

Lastly, will the following prejudice my application?
- We've been away from Singapore for 15 years and are only looking to return now
- That my children are non-Singaporean because I didn't take up citizenship for them

Many thanks,