Statement I : Tin in +2 oxidation state is oxidising agent.
Statement II : A substance which undergoes oxidation is oxidising agent

(1) For IV A group elements
Common oxidation state is : "+4"
C shows :- +4 , -4
Si:- +4 [Stable]

$$\begin{gathered} \mathrm{Ge},\mathrm{Sn}\left.\begin{array}{r} \\ \end{array}\right\}- +2, \underset{\mathrm{Stable}}{+4} \\ \mathrm{Pb}: - \underset{\mathrm{Stable}}{+2} +4 \end{gathered}$$

→ For Ge,Sn +4 is stable oxidation state hence in +2 oxidation state they acts as reducing agents
→ Where as for Pb '+2' oxidation state is stable [due to inert pair effect] hence in +4 oxidation state Pb acts as oxidising agent
→ Higher oxidation state is due to involvement of ns and np electrons
i.e., 

Lower oxidation state is due to involvent of only np electron
i.e., ns² np⁽²⁾ ⇒ +2
Higher oxidation state stability dcecreases from top to bottom

$$\begin{gathered} {\mathrm{Ge}}^{+4}>{\mathrm{Sn}}^{+4}>{\mathrm{Pb}}^{+4} \left[\mathrm{Stability} \mathrm{order}\right] \\ {\mathrm{Ge}}^{+4}<{\mathrm{Sn}}^{+4}<{\mathrm{Pb}}^{+4} \left[\mathrm{Oxidising} \mathrm{power} \mathrm{order}\right] \end{gathered}$$
Lower oxidation state stability increases from top to bottom
Ge⁺² < Sn⁺² < Pb⁺² Stability order

(2) The substance which undergoes oxidation is acting as reducing agent

The substance which undergoes reduction is acting as Oxidizing agent