Normal. It happened to me at AOS stage. Biometrics were taken before the interview despite I submitted them earlier in the process. I haven't filed gor N-400 but I'd imagine it would be the same.
Of course. ID documents such as passport, EAD, re-entry permit, Green Card is a US government property, not your property. If government asks you to return them, you should. It may not be taken at oath, but you should at least bring them.