I updated my game to version 1.8 so i cant speedrun anymore can someone help me.

Version 1.8.0 is very recent and with the Switch 2 release, a lot of changes are being discussed right now, so the new rules might take a bit long before coming. However it is certain that the newest version will still be allowed in the next rules, so even if there's a lot of uncertainities at the moment, you can still speedrun in your version. By the way if you're wondering what the 1.8.0 great plateau route is, it's the one from before BLSS was discovered.