The 747 classic can lose all hydraulics, like the one in Japan did, when the vertical stab was blown off. All fluid was pumped out of all systems when the lines were cut. Boeing offered, for a price, a fuse for the #4 system, to retain at least that system in the unlikely event of a similar failure. Not all airlines have bought it, so many classic 747s are still liable to the total failure of hydraulics. The 747-400 has the fuse, so it will not lose system #4 in the event of damage, provided the damage occurs after the fuse (which works by detecting unusually high flow rates and shutting off at that point, like an electric fuse does).
The classic also has a backup pitch control, using electrical power and the trailing edge flaps, but very few classic pilots I have worked with are aware of how it works. The Japan Airlines crew did not know, again an assumption on my part.
If the sim is to be believed, the loss of all engines will not result in hydraulic failure in the 747 and the 744; all four systems will continue to operate, even if the electrics and pneumatics are also lost, and since the flight controls are mechanically linked to the FCUs, the airplane can still be flown. I would expect the rates of control movement would be reduced as speed falls off, though.
The 777 is. like the Airbus, fly by wire, so it also needs electrical power. It has, I believe, some mechanical backup to one elevator and one aileron, but I don't know for sure. I think that the Airbus would be not so well off in the event of electrical failure.