Currently the first rank is 11 cases, and the second rank is 20 additional cases.
The second rank covers WHERE with numbers, strings, dates and timestamps, IN, BETWEEN, AND and OR.
Check out the guide tab in the game - it covers everything supported so far.
Once you finish that, you go into practice mode where you're randomly asked the same kind of cases like the previous ones.
I plan on adding support for GROUP BY, aggregate functions, HAVING, aliases, JOINING multiple tables, and some more stuff with more complex cases to match.
And the 6 months countdown doesn't begin until the game development ends so you're enjoying longer access.
I think it would be more compelling to see how much more material there is, or at least how much is planned, like a timeline or map. I'm a little hesitant to purchase it blind.