#3: Bitcoin is integrated to a side chain called RSK, which is Turing-Complete (like ethereum), and by using a Hardware Security Module architecture, up to 40% of the biotcoin miners lock the bitcoins to be issued in the side of RSK, in an algorithm called "the bridge", you can retrieve your bitcoin through this bridge by the smart contract by the RSK side. For more info take a look on the technical documentation about RSK: https://developers.rsk.co/rsk/rbtc/conversion/networks/mainnet/

Just to clarify, the miners secure the chain via Bitcoin poW. There is no hardware module involved. Also, its much more than 40% of the miners. Right now, its between 60-70%.