21. What is a Vue instance?
22. Which method is called when a Vue instance is created?
23. How do you create a new Vue instance?
24. Which option is used to specify the HTML element that a Vue instance will be mounted to?
25. How can you access the data properties of a Vue instance?
26. Which lifecycle hook is triggered before the Vue instance is destroyed?
27. What does the data option in a Vue instance contain?
28. Which method is used to watch for changes in a data property of a Vue instance?
29. What is the purpose of the methods option in a Vue instance?
30. How can you access the Vue instance itself within its own methods or lifecycle hooks?