Which is the correct formula of the Wilkinson catalyst?

Among the following,which is not the $\pi$-bonded organometallic compound?

The correct statement$(s)$ regarding the binary transition metal carbonyl compounds is (are) (Atomic numbers: $Fe = 26, Ni = 28$)
$A$. Total number of valence shell electrons at metal centre in $Fe(CO)_5$ or $Ni(CO)_4$ is $16$
$B$. These are predominantly low spin in nature
$C$. Metal-carbon bond strengthens when the oxidation state of the metal is lowered
$D$. The carbonyl $C-O$ bond weakens when the oxidation state of the metal is increased

An organometallic compound amongst the following is

Which of the following statements is incorrect?
$(1)$ $Al_4C_3$ is an organometallic compound.
$(2)$ Metal carbonyls are organometallic compounds.
$(3)$ $TEL$ (Tetraethyl lead) is a $\pi$-bonded organometallic compound.
$(4)$ Frankland reagent is a $\sigma$-bonded organometallic compound.

Which of the following is an organometallic compound?