Why is Test Case #3 hidden and locked.

Question

Why is Extra T. Coding Challenge question #3 locked and hidden?

Answer 1

Some of the hidden test cases are edge case, etc.

Here is a learning material about Software Testing
https://youtu.be/goaZTAzsLMk

Answer 2

I finished the software testing video and go to the coding challenge (Extra Terrestrial) and test case #3 still locked! What do I do?