1. Yes, Maximum of all the Decomposition reactions perform endothermic process only.
2. When quick lime is added to water, exothermic energy that is heat is evolved out by forming Calcium Hydroxide
CaO+H2O ------> Ca(OH)2
3. The curd contains lactic acid and the sour substances contains the acids like citric acid. these acids are easily reacts with the metals like copper and brass alloy's. because if the reaction takes place then the substances will be spoil. so these type of substances are not store in brass and copper vessels.