Use case for multiple inputs in a single transaction

Question

Is there a way to ascertain a pair or more of Bitcoin addresses belong to the same wallet on the basis an address pair was used as input for a single transaction?

Can I verify the address pair input is not part of a createrawtransaction or fundrawtransaction transaction, for instance from a blockchain explorer?

In which case besides createrawtransaction and fundrawtransaction would multiple inputs within a single transaction belong to different wallets?

Answer 1

Is there a way to ascertain a pair or more of Bitcoin addresses belong to the same wallet on the basis an address pair was used as input for a single transaction?

No.

Assuming that all inputs to a transaction are from the same wallet is often called the 'common input ownership heuristic', but it is possible to create transactions using inputs from various wallets, so there is no way to apply this heuristic with 100% accuracy. In many cases it may work, but in many cases, it will fail.

Can I verify the address pair input is not part of a createrawtransaction or fundrawtransaction transaction, for instance from a blockchain explorer?

No, the transaction data that is broadcast to the network is purposefully devoid of information about which software/method was used to craft the transaction. In some cases 'transaction fingerprinting' can be used to make an assumption about this, but again it is only a guess at best, false positives can easily be created too.

In which case besides createrawtransaction and fundrawtransaction would multiple inputs within a single transaction belong to different wallets?

A transaction with inputs from multiple wallets is usually referred to as a coinjoin transaction. Some examples of wallets that implement coinjoin transactions are Wasabi wallet, or Join Market. Other ideas exist to create 'payjoin' transactions, such as P2EP. Coinjoins can also be manually created using software such as bitcoin-core.