user26859: I don't seem to be able to ask the right question in the title, the way I asked the question is not correct.
What I really want to know is this:  
I can spend an unconfirmed output, then I can spend the output that spends that unconfirmed output, and I can spend that output, too, and so on...  
My question is: how many times can I do it?  

Edit: I just tried it in the testnet, I got this message: 64: too-long-mempool-chain. Is this 64 an universal number?
Edit 2: It turns out 64 is the error code. The actual number is 25.

user48884: There is no limit in the consensus rules about that. However nodes have a local policy rule about this. In Bitcoin Core, the limit is 25 unconfirmed transactions. This limit is user configurable.

26859: <p>I don't seem to be able to ask the right question in the title, the way I asked the question is not correct.<br>
What I really want to know is this:  </p>

<p>I can spend an unconfirmed output, then I can spend the output that spends that unconfirmed output, and I can spend that output, too, and so on...  </p>

<p>My question is: how many times can I do it?  </p>

<p><img src="https://i.imgur.com/gZiM2kL.png" alt=""></p>

<p><strong>Edit:</strong> I just tried it in the testnet, I got this message: <code>64: too-long-mempool-chain</code>. Is this 64 an universal number?<br>
<strong>Edit 2:</strong> <a href="https://github.com/bitcoin/bitcoin/issues/10004#issuecomment-345383285" rel="nofollow noreferrer">It turns</a> out 64 is the error code. The actual number is 25.</p>
 48884: <p>There is no limit in the consensus rules about that. However nodes have a local policy rule about this. In Bitcoin Core, the limit is 25 unconfirmed transactions. This limit is user configurable.</p>
