In which of the following ions is $p\pi - d\pi$ overlap present?

The $d_{xy}$ orbital can form a $\pi$ bond with another $d_{xy}$ orbital along which axis?

Match the orbital overlap figures shown in List-$I$ with the description given in List-$II$ and select the correct answer using the code given below the lists.
List-$I$:
$P$. Two $d$-orbitals overlapping axially with same phase.
$Q$. $A$ $p$-orbital and a $d$-orbital overlapping laterally with same phase.
$R$. $A$ $p$-orbital and a $d$-orbital overlapping laterally with opposite phase.
$S$. Two $d$-orbitals overlapping axially with opposite phase.
List-$II$:
$1$. $p-d$ $\pi$ antibonding
$2$. $d-d$ $\sigma$ bonding
$3$. $p-d$ $\pi$ bonding
$4$. $d-d$ $\sigma$ antibonding
Codes: $P \quad Q \quad R \quad S$

State the resemblance and difference between $\sigma$ ($\sigma$) and $\pi$ ($\pi$) bonds.

Which of the following combinations does not form a $\sigma$ bond?
$(i) \ 2p_y - 2p_y$
$(ii) \ 2p_z - 2p_z$
$(iii) \ 2s - 2p_x$
$(iv) \ 2p_x - 2p_x$

Which of the following statements is not correct?