Thanks for all the advice, folks! But I confess that my question was half-ironic.
My asking, "How am I to know which version of Windows I have / How can I find out?" is analogous to my 95-year-old maiden aunt asking, "The auto repairman says I need a new 'carburetor' - whatever that is! I suspect he's lying; how can I check that myself?" and my replying with some perfect technical explanation.
You folks don't seem to appreciate the irony: Anyone asking such an elementary question simply won't understand your answer.
Regards,
But how am I to know which poster is asking something half-ironic (or 25% or 75%)? How can I find out? 🙃