I think the 3/1 and 3/31 dates are errors that someone forgot to change from whatever boilerplate template they were using.
As for the other question, you just unlock the paint job, not the bike. You still have to buy the bike itself in the drop shop. I’m not sure what happens, though, if you unlock the paint job but are not at a level where you can ‘buy’ the bike. Will the paint job be there waiting when you are able to buy the bike, or will Zwift have forgotten that you earned it? Hmmmm.