The stability protocol, including the exchange
What the protocol does with data feeds from Oracles
Adding or removing stablecoins
Whitelisting stablecoins (or other ERC20s) for use in paying gas fees
The identity protocol, including how phone number attestations works
Linking of signers and off-chain metadata (e.g claims) to accounts
Most of Proof of Stake protocol, including elections, locked gold, slashing parameters
On-chain governance itself
MinimumClientVersion
BlockGasLimit
IntrinsicGasForAlternativeFeeCurrency
The protocol by which nodes communicate
The format of block headers, block bodies, the fields in transactions, etc
How nodes sync
How nodes store their data locally
Most parameters that affect the blockchain