Assertion :Tin (Sn) exhibits +2 and +4 oxidation states only and not +3 oxidation state. Reason: Inert pair effect of electron pair in s-orbital is responsible.
Down the group 14, the oxidation state +2 becomes common such as SnCl2,PbO and Pb2+.With tin, the +4 state is still more stable than the +2, but by the time you get to lead, the +2 state is the more stable and dominates the chemistry of lead.
+3 is not stable because of the Inert pair effect of electron pair in s-orbital.
In CH4 carbon is not in +4 but is in −4 state as carbon is more electronegative than hydrogen.