The legal operating limits for flight and cabin crew (CAD371) can be found in CAD's website
http://www.cad.gov.hk/english/flightstandards.html
According to Section 32 (for cabin crew), the cabin crew who starts work between 8am to 1pm can have a maximum flight duty period (from reporting work to engine off) of 14 hours 15 minutes for 2 sectors.
So for a 1005h departure and 2045h arrival, plus a typical 90-minute preparation time, the duty should last for 12 hours 15 minutes. An hour delay should be fine I guess?