The game version should be build 20 or a newer development version. Make sure to take care that every player in a match uses the same game version.
If two players could not agree on the version, what would happen? It might have some advantages if build20 would be the only version for the tournament. Replays don't get quickly useless and nobody who wants to watch has to change versions.
So far, it never happened that two people could not agree on a version.
As for compatibility, iirc replays were always compatible until somewhere around build 19, when backwards compatibility was broken to update some code. soo, whether we use core or trunk, should not matter as far as compatibility goes, and won't matter until some specific pieces of code are touched again. Correct me if I'm wrong.
The search gives this result
i tried the search function, got no results. Must have misclicked something.