Can USCIS look beyond the documents I submit or contact my employer, landlord, bank, or other people?

Yes. USCIS can compare your filing with information from its own records, other government systems, public sources, and investigative work. Whether the agency contacts a particular employer, landlord, bank, or other private party depends on the individual case. The practical lesson is that an immigration filing does not exist in isolation. Make sure the current filing is accurate and consistent with information that can be verified elsewhere. Prior filings, addresses, employment, and other verifiable facts can all become points of comparison.