i don't know the specifics of that challenge so i can't answer the title. lesson one is not that long though, so it wouldn't hurt to go back to it if you aren't confident.
Habari! Don't bother about that. This just may happen. Just keep learning!
I'd try to continue. But I always go back and repeat earlier lessons, to keep updated and to keep the basics fresh. Depends how confident you feel I guess!