A substance which gives a brick red flame and breaks down on heating to give both oxygen and a brown gas is

${\mathrm{CaCO}}_3,\mathrm{Ca}{\left({\mathrm{NO}}_3\right)}_2 \} \mathrm{Both} \mathrm{gives} \mathrm{brick} \mathrm{red} \mathrm{colour} \mathrm{on} \mathrm{exposer} \mathrm{to} \mathrm{bunsen} \mathrm{flame}$

IIA group nitrates undergoes decomposition similar to that of LiNO₃
Where as CaCO₃ on decomposition gives CaO & CO₂
 

Therefore option 4 is correct