$A$ molecule of ammonia $(NH_3)$ has

What is the role of the metal or reagents written on the arrows in the given chemical reactions?
$(a)$
$(b)$ $CH_{3}COOH + CH_{3}CH_{2}OH \xrightarrow{Conc. H_{2}SO_{4}} CH_{3}COOC_{2}H_{5} + H_{2}O$
$(c)$ $CH_{3}CH_{2}OH \xrightarrow[Heat]{Alkaline KMnO_{4}} CH_{3}COOH$

$A$ colourless gas '$X$' has a formula $C_{3}H_{6}$. It decolourises bromine water. Write the chemical name of '$X$'.

The suffix $-ol$ is attached to which functional group in nomenclature?

Which of the following is the reaction occurring between alcohol and carboxylic acid in the presence of concentrated $H_{2}SO_{4}$?

Explain the following reactions with chemical equations:
$(i)$ Oxidation
$(ii)$ Hydrogenation
$(iii)$ Substitution