Hey,
you'd have to reinstall the game to get 1.2, assuming you used a disc then you'd be on version 1.2 straight after install.
If not, check out
http://forum.helloclan.eu/bfv/future
1.2 is easier, as it's the version the game came out on eventually. I can get new people straight into it without having to worry about patching etc. As there are no major differences in the versions, it makes no sense to try force everyone here to upgrade.
In terms of having both, install version 1.2 then copy all the files to another folder, then patch the first install to 1.21
You'll have both versions of the game then, just run the exe for the version you wish to play.
Hope this helps, but if not then let me know.
Regards,
SucceededKiller