Hi Kasia, yes it is the beam but here there are two beams joined together instead of a single beam. Also, are those die chips on top of the right side of the beam?
Errors of Lincoln Cabin I don't know, I am not experienced enough to say. I did look (quickly) at images for LINCOLN CENT CABIN and there are at least two doubled die for the cabin, I saw pictures, so if you google that and do images, see what that is. Maybe there are more. Or someone else here who can tell will get to you on this. Best to you.
It looks to me like there could be small die breaks. Also, on your question about the design, what's helpful for me is to find another coin in approximately the same die state and strike to compare to in hand. It's much easier than trying to do it through pics.
Can you notice the difference between the two coins on the left as against those on the right? Your comments please. Thanks