In which compound is the oxidation state of phosphorus $+4$?

Which of the following statements is not correct?

$A$ compound contains $x$,$y$,and $z$ atoms. The oxidation number of $x$ is $+3$,$y$ is $-5$,and $z$ is $+1$. The possible formula of the compound is:

$LiCoO_2$ crystallizes in a rhombohedral structure. Consider a situation where $50\%$ lithium $(Li)$ is extracted from the lattice. To keep the crystal electrically neutral, the change in the average oxidation state of $Co$ is

What is the oxidation number of $Cl$ in bleaching powder?

What is the change in the oxidation state of $Mn$ in the reaction of $MnO_4^{-}$ with $H_2O_2$ in acidic medium?