By default, the top-level page for this wiki (http://wiki.onosproject.org) documents the up-to-the-moment current development branch of ONOS ("master" or "ONOS Latest"):

ONOS Latest

Documentation for each official release is archived in its own space:

ONOS 1.5 (Falcon)

ONOS 1.4 (Emu)

ONOS 1.3 (Drake)

ONOS 1.2 (Cardinal)

ONOS 1.1 (Blackbird)

ONOS 1.0 (Avocet)