Hey there, new speedrunner from the Netherlands here, looking to grind myself some WRs :). I was reading the rules on IL runs ( https://www.speedrun.com/st/The_journey_begins#0.6.x to be precise), and wondered about this one:

"Some levels require you to show the black screen at the beginning before finishing a level. Those will be stated."

and further on:

"Some levels require you to show the black screen at the beginning and at the end."

What black screens are meant here, and which levels do these rules apply to?

When you click on a level in the individual levels tab, you can click on category rules. In there, it should state if you need to show the black screen at the beginning of the level or not. This is because some levels have a cutscene that ends the level at the end, without showing the In-game-timer that most levels to, alongside the stats for the level. This window is crucial for verification. In other words, we need to see the black screen before the level because it shows your best time, and then we need to see the world map after your run because it shows your best time. If there is a change between those two times we can verify if your time changed, hence an actual PB. Some people might just get a really good time off camera, record a run, and pretend that run they just got resulted in their world map time. For some levels in the forest world, 0.6.0 Nolok's castle, and some others, this rule is needed.

So in order to submit powerupless runs / runs without PB for those levels you should reset your in-game PB statistics, to show the difference of pre-run and post-run PB?

Yes, pretty much. Also, for Nolok's castle runs on 0.6.x, you're not allowed to do the Cutscene stat overlay glitch since it always results in an in game time of 48.01... and obviously that removes all skill needed to run nolok's castle, so It's best without that glitch. it would of course be allowed for full game runs.