Which of the following statement(s) is/are incorrect?
1) Boron shows +1 and +3 oxidation states
2) Sn⁺² is more stable than Sn⁺⁴ 
3) Tl⁺³ is more stable than Tl⁺¹ due to inert pair effect
4) Pb⁺⁴ is a stronger oxidising agent than Pb⁺²

a) Due to small size of boron, the sum of it’s first three ionization enthalpie’s is very high
b) This preent is it to form +3 ion's
c) As we move down in group 13, due to inert pair effect the tendency to exhibit + 3 oxidation state decreases
d) The compounds in +2, Oxidation state are covalent in nature (fajan rule)