oxides of lithium and magnesium are less soluble in H2O. also the hydroxides of both decompose at high temperature.
2LiOH→Li2O+H2O
Mg(OH)2→MgO+H2O
(ii) Nitrides is formed from both the lithium and magnesium when they react with N2.
6Li+N2→2Li3N
3Mg+N2→Mg3N2
(iii)Neither Li nor Mg form superoxides or peroxides.