Lithium and magnesium in many respect behave in identical manner. Which of the following facts does not describe the correct behaviour of Li and Mg in comparison to the other alkali metals?

Carbonates and hydroxides of Li and Mg decompose on heating to give oxides whereas those of other alkali metals remain unchanged on heating

LiCl and ${\mathrm{MgCl}}_2$ are soluble in alcohol whereas chlorides of other alkali metals are insoluble

Nitrates of Li and Mg decompose to give oxides on heating whereas those of other alkali metals decompose to give nitrites

Li and Mg give peroxides on heating with oxygen whereas the other alkali metals give oxides.