Musk made it clear that Starship is not SSTO, but he plans to fly it suborbital point to point like an airliner. SpaceX is already advertising for someone to design the offshore launching and landing platforms.
He does now, although he also says it will technically be capable of SSTO, but (not surprisingly) can't carry signficant payload. In one of the many vids of him talking about the ongoing design he definitely said it was SSTO.
The system requires two launches of complete stacks in order to put together a Mars shot (or probably a Moon shot as well), which interestingly is the conclusion Von Braun came as a consequence of Apollo development and deployment. VB's estimate was twelve Saturn V stacks to construct a single round-trip Mars mission, IOW, the entire lunar program to make one trip to Mars. I wish NASA had tried it, but am also a little glad NASA didn't, because it seems likely that it wouldn't have been repeated even if successful.
After that success (or maybe failure) the Shuttle (which wound up years behind schedule) might have turned out differently and been a better design, cheaper, more flexible, with a crew-sized craft, smaller capacity launch system, and retain the Saturn V for space station component and other cargo-only launches. End-to-end cost of fitting the single Mars mission and construction of a US-only large permanent space station, plus the access to and from orbit for station crew rotation and perhaps science station on the Moon would have been more fruitful and probably cheaper.