> I think the first public version was released in 2012, or late 2011.

The first public version of Timberwolf, which was a port of Firefox 3.5, was released in June 2010:

http://www.amigabounty.net/?function=viewhistory&projectid=44&historyid=41
https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=7141&forum=9

After this, Timberwolf switched to Firefox 4.0 (originally called 3.7) code base:

http://www.amigabounty.net/?function=viewhistory&projectid=44&historyid=49

The second public version (4.0.1) was released in February 2012:

http://www.amigabounty.net/?function=viewhistory&projectid=44&historyid=57
https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=8325&forum=9