Yooka-Laylee and the Impossible Lair has a wildly inconsistent difficulty curve. Most of the game is breezy platforming, and then the final challenge is a grueling gauntlet unlike anything before it. You can attempt the Impossible Lair immediately after starting, but you probably won't get far. The whole premise of the game is to play all the other levels to gather bees, which act as extra health points during the Impossible Lair.
A day before Yooka-Laylee and the Impossible Lairactually releases, someone has already tackled the Impossible Lair without any bees. Speedrunner horheristo has uploaded a video where they clear the game in under half an hour without the help of the Royal Stingdom's Beetalion. It's a master class in pattern memorization and platforming prowess. (The Impossible Lair part begins at about 4:30; the previous stuff is the game's intro.)
It's not perfection, though. Horheristo takes damage six times throughout the course of the run. Because they haven't acquired any bees, this causes Laylee to start fluttering around -- the couple-second window when you can grab her back, thus negating any damage you've taken. These missteps are understandable. Capital B's hitbox during the boss fight sequences feels kind of wonky.
There are rewards aside from bragging rights. There's a secret ending (as shown in the video) where Yooka and Laylee dismiss this sort of perfection as nothing more than fantasy -- a fable because it's too good to be true. Also, it's the key to unlocking one of the game's 62 tonics. Completing the Impossible Lair without losing any bees grants the Golden Try tonic, which doubles all quills earned in a chapter and paints Yooka and Laylee gold. Lastly, there's a special medal at the title screen.
However, these rewards mean that Yooka-Laylee and the Impossible Lairwill have an absurdly low rate of people who hit 100 percent completion. One of the achievements/trophies is for collecting all tonics (and then there's another for purchasing all the tonics, and yet another for earning all other achievements/trophies). If Golden Try is only earned by not losing a single bee, even horheristo would be a long ways off from getting it. They'd have lost six bees during that incredible run. Only people who beat the Impossible Lair before playing the rest of the game will be afforded any leeway when it comes to a no-damage run.
Nevertheless, it's an astounding accomplishment. Most people will struggle to make it through the Impossible Lair at all, nevermind doing it with this sort of mastery. Horheristo can be proud of the fact that they're likely the only one running around with Yooka and Laylee dipped in gold.