Great questions but I'm not sure how these questions lead to a definitive diagnosis. The following link written in 2014 speaks to the difficulty of diagnosing PMR. I don't think anything has changed in ten years except more research has been done specifically with biologic therapy.

"One of the challenges in the diagnosis of PMR is the lack of any diagnostic tests that are specific for this entity. Additionally, given the multitude of other conditions that can mimic this diagnosis or present with polymyalgic symptoms, the diagnosis requires exclusion of other conditions."

The conclusion is spot on ...

Conclusion
PMR is a common inflammatory condition affecting individuals aged 50 years and over. There is a close association between PMR and GCA. Given the absence of any diagnostic tests specific to PMR, careful consideration should be given to excluding other mimics, particularly SpA and RA. Ultrasonography of affected joints may complement the clinical evaluation for the diagnosis of PMR. Treatment consists of prolonged GC therapy, but relapses are common. Moreover, GCs are associated with significant morbidity. Evaluation of therapies targeting inflammatory cytokines as alternatives to GCs in PMR is underway.