[Sarah Barracuda]

At 45,000 feet, could the passengers still breathe or would it have made it impossible for them to breathe, even with the oxygen masks

[Yosemitest]

If the cabin pressure was still maintained by the flight crew, they could breath.
If the flight crew (the pilot and copilot stealing the aircraft wanted the passengers asleep or less of a threat, then they would "foul the air".
But I don't know the capabilities of the Boeing 777 in that respect, that IF they "foul the air",

THEN would it automatically drop oxygen mask,
and IS the cockpit air and the passenger compartment air on different systems.

But to solve this mystery we need to focus more on the pilot and copilot.

I would want to know more about the computer history of the personal 777 flight simulator that Captain Zaharie Ahmad Shah self-built.

What was the most practiced route he flew with his simulator?

What was his most common practiced landing destination?

Does the government have that simulator to gleam all the history it can off of it ?