How many kings did Sparta have at once, and from how many royal houses?

Two kings, one from each of two royal houses

An unfree, state-owned population who farmed the land of the Spartiates

What was the krypteia?

A secret operation in which young Spartans killed helots to keep them cowed

It was compulsory for full citizenship, requiring a food contribution from one's land

Persian money funding a Spartan fleet, used by Lysander

Because much of it comes from admiring or much later, idealising sources

10questions. Pick an answer and you'll see why right away.

How many kings did Sparta have at once, and from how many royal houses?
Which element of the constitution did Aristotle regard as having near-tyrannical power?
Who were the helots?
What was the krypteia?
At what age did a Spartan boy enter the agoge?
Why was membership of a syssition important?
What did Aristotle claim Spartan women had come to own by his day?
Who captured Amphipolis for Sparta in 424 BC?
What was decisive in allowing Sparta to defeat Athens at sea?
Why must the 'Lycurgan' picture of Sparta be treated critically?