Good question, mate.

In Bitcoin, a transaction ID (or txid) and transaction hash are essentially the same thing. The txid is just a hash of the transaction data. It's used to uniquely identify transactions in the blockchain.

As for your second question - nope! Each transaction has just one unique txid/hash. This gets created when the transaction is made, and it doesn't change.

So whether we're talking about blocks or transactions, there's always just one PoW or one hash/id respectively!