Whose or who’s?

"Who’s" and "whose," often used to form questions, do not mean the same thing.

This is the contraction of who is or who has. If you can write the sentence with who is and the meaning doesn’t change, it’s a contraction.
Whose is the possessive form of who or which. Whose can apply to inanimate objects unlike who’s.
Who’s that lady in the red dress?

Who’s ready to party?

Cindy, who’s my aunt, can’t make it tonight.
Whose hat is this?

Whose essay was the best?

The wooden door, whose engraving is elaborate, is over 100 years old.