Hints - The Key Is Going Slow And Steady

Click hints to reveal.

Hint to start puzzle: The diagram, sometimes called a dichotomous key, has 26 endpoints. Treating No as 0 and Yes as 1 should help you get started. And make sure to check your work! Answering any of the five questions incorrectly will give you the wrong letter. If you submit intermediate phrases, the site will confirm whether they're correct.
Hint for extraction: These pets are all so cute. They make me want to burst out into song! Use that as an ordering, then use one more number to decrypt.