Yes. The "stops" function to shut off the flow of air through the reeds. Thus, you can play one set of reeds for a specific sound, or both for a more robust sound.
it will differ from maker to maker. I believe that Hohner usually has them up on their German made one rows, though if you look at the other big market makers like Gab or Cast (or the Chinese made Ariette) they usually have their stops down to play. Just a design difference, not going to affect how you play. I assume that its easier to make it that way and uses less material so it makes sense for the large producers to do it that way. Typically I grab my stops when picking up and putting down the accordion so having them up is a good thing design wise, but that does mean that they can get damaged if you aren't careful.
How do I adjust the thumb strap, it's not attached with a screw it's more like a rivet. I think it would be easier for me if it were a little tighter. Also the strap on the bass side is loose too but it uses screws to attach it, so shouldn't be a problem. Thanks