S3_3-alpha2 is commit a05f44d044f5dab2bdb0fea9515a33b90b158871 in freeciv git.
Version number in that commit is 3.2.94-alpha2

There has been no datafile format freeze nor network protocol freeze in
freeciv S3_3 yet. Alpha2 compatible datafiles are not going to be compatible
with final freeciv-3.3, nor will alpha2 server/client be able to interoperate
with final 3.3 server/client.