Actually, the apostrophy here is incorrect. Since "it's" is a contraction of "it is" or "it has", it cannot be placed at the start of those sentences. "Its" is possessive, which is what Pelin was trying to say. So don't use apostrophes here :)

Don't forget to put in apostrophes. I like it's smell It's smell is good/nice - it would be more natural to say' it smells nice' It's smell lingers in the room (is a better way to say this.) It's smell is long-lasting

Yes, all of these are correct :)