Thanks. Based on the number on the frame, it's from January 2015.

Turns out I might not need a rear derailleur since the Alfine CT-S500 chain tensioner is able to handle two chainrings. But I'll need to add Pacific Cycles' front chain tensioner since the chain tends to fall off when folding the bike.

If the headset does need adjustement, how is it done?

Does it do the same on your Birdies? https://gofile.io/d/8Cq8Ns