The B747 is no problem to fly with two engines out in the worst condition- ie on one side. It is periodically practised in the simulator. If it happened in the cruise, the resulting drift down altitude is pretty seriously compromised-some 17,000' at max top of climb weight up to mid 20,000s' at more typical cruise weights. A diversion would then be recommended.
It is known that a 747 will fly on one- not very well, but it is surviveable.
Large aeroplanes do not use limited flap landing settings- it can create more of a problem stopping. Twins do.