1.02 - the officially final version by developer. Has additional content, including small locations, the companion-dog and some easter eggs. It's a 'Fallout: Nevada - Fixed edition' with english translation (with narration) and sfall, configurator, IFP, HRP and many bug-fixes. 0.99a - first major version, released in april, 2011. 0.99c- test-version for limited number of users. Content also differs by ~ 30-35% (plot, some dialogs, some quests, differences in locations and endgame bosses.)
The plot slightly differs (it's about search for the 'SoS' system). Basically, version 1.02 with restored content and loads of bug-fixes. It's a 'Fallout: Nevada - Fixed edition' with english translation and narration, sfall, configurator, IFP, HRP and many bug-fixes.