treif keilim

Despite stam keilim being eino Ben yomo, why are we not required to use kashered cookwear when dining out? Similarly, if I rent an airbnb that comes with cookwear, do I have to kasher the cookwear before using it?

glatt kosher

If I wanted to keep glatt kosher, how would I go about doing it? My understanding is that “glatt” is just a marketing term and doesn’t actually mean anything when they write it on the hechsher (eg chicken is labelled as glatt). How would a kosher...

glycerin

Wikipedia says that glycerin has a sweet taste. If glycerin is an ingredient, do you have to assertain that it’s from a vegetarian source?