Why can the same contract code be deployed unchanged on several chains?
When using EVM-compatible chains, the addresses may look the same, but make sure you know which chain your assets are on.
Put simply, once a contract is deployed, its bytecode is fixed and anyone can view it. Whether the source code is readable depends on whether the developer has verified it on a blockchain explorer.
When you call a contract on Ethereum, the EVM charges Gas for every instruction it executes, paid in $ETH .

This information is for reference only; don't take it all at face value.