Misc: In 1974 Landslide in ---------- Province Peru creates a natural dam.?

Questions

What is the name of the Russian Czar's daughter who might-or might not-have survived the Russian revolution?

What was the instrument of execution during the 'Reign of Terror'?

What was the name of Plato's school?

What was the name of the B-29 used at Hiroshima to drop the bomb?

What was the nationality of the prisoners in the 'Black hole of Calcutta'?