1: You are not prohibited from working with Russian developers who currently reside in Russia. The biggest issue is figuring out a way for you to pay them, but that sounds like its being taken care of by the company.
2: You ARE prohibited from exporting consulting services to Russia, to either physical or legal persons, for "enterprise management software and design and manufacturing software": https://ofac.treasury.gov/faqs/added/2024-06-12#:~:text=1407...
3:Just contact OFAC. They are responsible for enforcement, and they have a hotline you can use.
Seriously though, you don't need this hassle.