Question on contract instances

[orthecreedence]

To my understanding, a contract is a WASM program (I'm assuming a hash of it). Does the key for this program contain metadata? In other words, can two instances of the same WASM program exist under different keys, but also (verifiably) running the exact same code?

Or can only one instance of a WASM program exist in any given network?

Following this, if multiple instances of the same contract are supported, would it be possible for two contracts to interact with eachother only if they share the same code (or some previous version of some known code)?

Thanks!