Would someone have any idea that at its last known position ie Igari .....How much fuel did the aircraft have since it was fueled to fly to Beijing with reserves ??
It is possible to estimate the trip fuel & therefore reserves etc. but the final fuel load would be the Crew's decision. It could have carried plenty more than the minimum required to get to ZBAA.
The only ones to know for sure are those in possession of the ground copy of the loadsheet. That would show minimum required fuel plus any extra.