An unknown compound $(A)$ (molar mass $= 180$) on acylation gives a product (molar mass $= 390$). Find the number of hydroxyl group present in compound $(A)$.

The product $(A)$ of the reaction is:

The product $(P)$ of the given reaction is:

Arrange the following compounds in increasing order of their property as indicated:
$(i)$ Acetaldehyde,Acetone,Di-tert-butyl ketone,Methyl tert-butyl ketone (reactivity towards $HCN$)
$(ii)$ $CH_3CH_2CH(Br)COOH$,$CH_3CH(Br)CH_2COOH$,$(CH_3)_2CHCOOH$,$CH_3CH_2CH_2COOH$ (acid strength)
$(iii)$ Benzoic acid,$4$-Nitrobenzoic acid,$3,4$-Dinitrobenzoic acid,$4$-Methoxybenzoic acid (acid strength)

The major product in the following reaction is