I have a second copy of version 1.5.7.8 with no mods installed, however the modded intro with the bar loading and the spaghetti icon at the bottom left are still there and i cannot figure out how to remove them. Would I be able to submit a run under these conditions, as technically there are no mods installed?

Thank you in advance!

Any runs with the spaghetti icon there will result in a rejection due to the modding Api still being installed, if you're using Lumafly as mod installer I've heard there's a "Launch vanilla" button in it that should launch the game in actual vanilla

unfortunately i am using scarab launcher, is there any file i can delete or any way to remove the api?

You should be able to use Steam to verify integrity of game files to undo all changes