The demo will include the titular Impossible Lair. Thats the first level you take on in the game, and the ultimate challenge at the end. Every normal level you complete lets you take an extra hit in the Impossible Lair, but you can tackle it at any time. As the name implies, the Impossible Lair is no joke, but you can theoretically beat the game just through this demo.
Source: N4G PC You can beat Yooka-Laylee and the Impossible Layer in its free demo but only if youre good