So this is becoming more and more common with Russians. They're getting subjected to extended AP, which is a type of background check carried out for national security reasons.
We just had a whole conversation about this in another thread, you're welcome to have a look:
1. I actually have no idea. Seems like you might need to contact the embassy and find out.
2. Good question. Tagging experts @milimelo and @jan22 for advice.
3. I do not believe AP has anything to do with USCIS. It is Department of State. More info can be found here: https://en.wikipedia.org/wiki/Security_Advisory_Opinion
4. No, it does not mean you are screwed. Every single applicant gets AP, some are just subject to extended AP that takes longer. It is actually very likely you'll eventually get approved and get the visa. The downside is nobody can say how long it will take. Can be days, weeks, months or even years. And there is a small chance that the visa will be rejected after review. It depends on if they find anything deemed to be a true security threat or not.