When chicks are little, sometimes their poo will stick to their bum and it can clog them up. If they cannot poo, they will die and when the poo sticks to their bum, it clogs them up so they cannot go. You'll have to wet it (baby wipe, paper towel, etc.) and slowly remove it or they won't make it.
Yeah, it's likely just from hatching and it didn't come off all of the way. If it's completelly dry, you can go ahead and do it...don't pull it, though! Just clip it a little.
Does it just look like, for instance, a placenta cord and not actual inside body parts? If so, you should be fine to...
Yeah, just leave it alone. It should dry up and then you can take scissors or finger nail clippers (sterile) and clip it close to the fuzz so the others don't peck at it.