The privatekeys are somehow within the blockchain. So you don't need a hard drive or another storage. As long as the blockchain exists you have access to the keys.
It is, but, you need to know it in order to access you wallet address if you are accessing your wallet on another device.
Our guess is that he knew that the early mined coins will be moved one day. So he created a 'prize competition'. Otherwise he could move the coins to quantum resistant P2PKH addresses, but he did not and is not doing.