Bitwarden isn't a microservice based architecture. It's just a service based. If you're using a shared database, it's not a microservice. Microservices each have their own database and then either through your API gateway, service discovery, message broker, etc each service queries the other service for the data it needs.
That’s a false statement. Microservices can share single database. In perfect world each microservice would have each own, but we’re far from perfect.
No it's not. That's what defines it as a microservice. If the services all talk to the same database, it's just a service based architecture.
No, because there’s really no single definition of microservices.