The SRBs were collected from the sea for reused and the upper stage was reused after landing horizontally. The only thing not reused was the upper stage drop tank. That single use drop tank was rather big, true, but not a rocket, not a rocket at all.
The Soviet lookalike did use a single use rocket as its second stage, with the reusable part just being an orbiter.
Interestingly, the Buran’s Energyia launch vehicle could possibly have been made reusable exactly because the tank and the engines were one unit. At the expense of payload capacity, of course. And anyway the Soviets were confused about the whole shuttle concept because it didn't seem to make economical sense, reusable booster or not – but they assumed the Americans knew something they didn't.
How would Energyia become reusable? Tail landing? Is there more to this, something specific that would make Energyia a candidate for tail landing other than just "if F9 can do it, in theory every liquid fueled rocket could do it"?
Wow, that's ... ambitious. I'd imagine the extra mass to make an energyia-size tank+engines able to land horizontally to be enormous. It's not just wings (plus folding mechanism, if you believe that's worth saving a bit of drag on the way up) but also landing gear plus all the structural strengthening required.
Sounds suspiciously like one of those projects you propose when you want something finer short term but assume that they never survive to the point where they actually need to deliver?
The Soviet lookalike did use a single use rocket as its second stage, with the reusable part just being an orbiter.