Anything's reusable if you throw as much resources into maintaining it as you would have rebuilding it every time. The Soviets just realized how stupid an idea that was. We didn't.
They did keep it around for the two things only it and shuttle could do: bring things back from orbit and execute single orbit missions (ie the cross-range ability to return to base after a single orbit.)
So did Buran itself. Its wing needed replacement after that flight. That's why it didn't flew with people in 1989 when it was still politically/economically possible. Then, it was too late.
More than once my friend. And if thing works - why should you care. Buran was a very top tech, superior to US shuttles in so many ways (capable of fully unmanned two-way trip for starters). The whole "Energia" complex is still unmatched by any spacecraft system in the world. The loss of this tech is unrecoverable though.
>capable of fully unmanned two-way trip for starters
Nope. Technology and precision required for fully-automatic landing of such aircraft becomes available only now. That particular landing was remote-controlled by a closely following plane.
Once. Does that even count as reusable?