I’m not an expert, but I think these are mostly accurate (or complete fabrications :))
1) JPA is the persistence technology for mapping entities to the DB. EJB3 spec is much broader and encompasses that idea along with the idea of container-managed transactions, bean pooling, load balancing and all that “enterprisey” stuff.
2) JP QL?
3) For EJB3 you need annotations, and the UML designer doesn’t generate annotated classes at the moment, so no.