I was just wondering how it was possible to send a Tx that was spending unconfirmed deposits (i.e. with 0 confirmation).
Why wouldn't it be possible? It would be very inconvenient if you have to wait for your change to confirm before you can send another transaction, and it would be impossible to use CPFP if you couldn't spend unconfirmed inputs.
If I remember correctly, I think you can do this up to 24 transactions deep. After that, the default mempool will reject your transaction.