I know a way to get alpha 1.2.0 going up (has to be new launcher), you go into your minecraft profiles and then you click edit profile then you should see 3 buttons in the middle each saying: Enable experimental developments versions (snapshots), allow use of old "beta" minecraft versions (2010-2011)
and allow use of old alpha versions (2010). So then there is a little box beside each of them, you want to click alpha, after you click that and below that there is a list of versions you want to click that and scroll down until you see alpha 1.2.0 you click it then you hit play and you're all good
and allow use of old alpha versions (2010). So then there is a little box beside each of them, you want to click alpha, after you click that and below that there is a list of versions you want to click that and scroll down until you see alpha 1.2.0 you click it then you hit play and you're all good