Which of the following statement(s) is/are incorrect?

1) Boron shows +1 and +3 oxidation states

2) $S{n}^{+2}$ is more stable than $S{n}^{+4}$

3) $T{l}^{+3}$ is more stable than $T{l}^{+1}$ due to inert pair effect

4) $P{b}^{+4}$ is a stronger oxidising agent than $P{b}^{+2}$