Is this about Starship the second stage, or only about the booster landing? Does a soft splashdown in the ocean count? Does starship have to get all the way to orbit, or is a suborbital flight enough if it's pretty much equivalent to an orbital one, like they're planning for the test flight?

Creator appears to be inactive but clarification would still be valuable, would asking mods be worthwhile?

It seems to me that Super Heavy Booster reaches space but doesn't reach orbit so has to be 2nd stage Starship.

While just 6 months might seem optimistic for 2nd stage catch, the late July plan for SH booster catch perhaps would indicate that 6 months would be pessimistic if that was sufficient.