But *ahem* back on subject, is it as easy as I think it is to go from Alpha 3 to 5, back to 3 and then up to 5 again?

Just a matter of applying the respective upgrade files and NOTHING else (other than syncs between Alpha 3 and 5)?

Furthermore, is it possible to go back down to v2.00-final from v3 as well, or are we stuck at v3 now?