The older versions have a compatible database except for the compact binary import group type.
If for some reason you want to run an older version after using compact binary import groups - v5.9.9.2 will revert the change.
Selected older releases for registered users:
v5.9.9.2 (64/32)
v3.7.4 (64/32)
v2.9.8 (64/32)
v1.9.9 (32)
