I suspect you're looking at outdated information - it did used to be 6 months. Follow the link I gave you previously, which says the following - "Police certificates expire after two years, unless the certificate was issued from your country of previous residence and you have not returned there since the police certificate was issued." https://travel.state.gov/content/travel/en/us-visas/immigrate/the-immigrant-visa-process/step-5-collect-financial-evidence-and-other-supporting-documents/step-7-collect-civil-documents.html
It's very odd that they're asking you to schedule the interview, and that they're asking the petitioner to do the medical. Can you give us the exact wording (maybe upload a copy of the email - redacting any identifying info)? These are the steps for an interview at Frankfurt usually (but only done after you receive the interview letter from NVC who schedule it for you) - https://travel.state.gov/content/travel/en/us-visas/Supplements/Supplements_by_Post/FRN-Frankfurt.html
When were you DQ'ed? I'm wondering if perhaps you missed the interview letter and original appointment and that's why you're having to schedule it now. If you could fill your timeline in (on your profile) it would be super helpful.
And what does your CEAC status say?