(a) Due to inert pair effect, Pb(II) is more stable than Pb(IV). Hence, there is no reaction between PbCl2 and Cl2.
(b) Due to inert pair effect, Pb(II) is more stable than Pb(IV). Hence, PbCl4 is thermally unstable and on heating decomposes to form PbCl2.
PbCl4Δ−→PbCl2+Cl2
(c) PbI4 does not exist due to strong oxidizing power of Pb(IV) and strong reducing power of I−.