Beethoven's trills begin on the upper note - as in the Waldstein, but also the late sonatas like op. 109, last movement - but in the instance you cite, there's an exception.
The stepwise descending melody necessitates that the trill begin on c - the ornament is around a passing tone, and repeating the starting note to the passing tone is unnecessary. Rhythmically, the emphasis falls on the passing tone, which is the real point, since ornaments are rhythmic accents in fact.
Taste is always the final arbiter, whatever the rules say - if you look at the ornaments in the Aria of Bach's Goldberg Variations, playing them by those rules - even the rules by Bach reprinted in the Kirkpatrick edition - are musically wrong and nonsensical, with the result that in all interpretations of that piece, the rules are politely ignored. But that's a larger discussion ...
Good luck with Op. 49, and if you're interested in playing Beethoven at this level, don't forget there are six Sonatinas which are beautiful and well worth studying and playing.
Claude always used to say that there were only two geniuses in music - "Beethoven and me."
But he also had a wicked sense of humor - peace, CD