" The stability of "+1" oxidation state increases in the sequence "

The tendency of Ge, Sn, Pb to show +2 oxidation state, increases in the sequence

Due to inert pair effect, the stability of +2 oxidation state increases on moving down the group 14. Why?

Explain the following : The stability of + 5 oxidation state decreases down group 15.

In group 16, the stability of + 6 oxidation state decreases and that of + 4 oxidation state increases down the group. Why ?

Stability of an oxidation state depend on

Why does the stability of + 5 oxidation state decrease on moving down the group ?