What is the L-word?

Why does the part before the comma need to be a complete clause?

Regarding who/whom 1) The relative pronoun is the subject of the relative clause => who. "John is the only one who understands me" 2) The relative pronoun is the object of the relative clause => who/whom. Whom is more formal than who.

." Mask

Prepositions that signify position in space block the use of reflexive pronouns. Therefore, it is correct to say "She pushed the cart in front of her" and not "She pushed the cart in front of herself."

Whose is the money that lies on the table? Whose is the money that is lying on the table? Could anyone please tell me the difference in meaning between these two sentences, if there is any.