In the past, I've leaned toward the first solution, for the reason that RubberDuck makes in his comment, however, having seen a few questions asked like this, now, I'm not so sure.
Consider Exhibit A and Exhibit B.
These are both swift questions that from some Stanford course intended to teach people swift. They're different questions from different users from the same assignment. And we really shouldn't be too surprised to see this same question repeated. There's even a good enough chance that you want to ask a similar question, I think.
The problem is that some will find issues the way the tutorial code is written and will want to review those parts. Having answered both of the questions I just linked, I can tell you that was the case for me. It was only easier to resist the second time, because I had already said "Oh yeah, we've been here before."
And the hard part of it is that as a reviewer, on the one hand, I think it's important to comment on things that the tutorial does wrong so that they can be improved upon, we can all understand why that code is wrong and how to write it better and move on.
But on the other hand, I don't want some review that I spent time writing and thinking about to be shoved aside by an asker who simply says "Well, I didn't write that part."
So, with that said, here's what I recommend...
If you are interested in potentially hearing comments about bits the tutorial code got wrong, then consider yourself the new maintainer of all of the code (and the author of just your code). Post it all. Make it clear what's yours and what isn't yours, but also make it clear that you're also interested in hearing feedback on the part that's not yours, as you'll be maintaining this code now and want to make the effort to improve it all (even the parts you didn't originally write).
If you are not interested in hearing comments about the parts you didn't write and only want feedback on how well you did the task the tutorial put to you, then you need to take a different approach.
You could post the whole code before your changes in the block quotes markdown, and then post the code you inserted below. Ultimately, having the original context will be important in answering the question, so it's important to have it accessible.