Questions about Kosher Food

Hey everyone! I’m not Jewish, but I have two questions of kosher food.

My first question is this. Do kosher foods have to show a certification or notice that the product, or menu or store is kosher certified (safe to eat)? If a product could pass as “kosher approved”, but it doesn’t have certification, can it pass as kosher?

My question comes from this observation. I was at a game with a friend recently, and as we were walking the concourse I noticed this concessions stand that is entirely kosher. The concession stand had a kosher certification in front of the two registers, which of course showed Hebrew and English writing. I ended up grabbing some food as apparently, this concession stand was the only place where 100% of the hog dogs are beef (other concessions offering hot dogs has some pork mixed with mostly beef), and I was only looking for 100% beef food.