What does the molecular formula $C_3H_9N$ represent?

$C_3H_9N$ represents

$90 \ g$ of ethylamine on reaction with methyl chloride produces a tertiary amine as the exclusive product. The amount of methyl chloride required is:
$[\text{Given atomic masses in amu}: H=1, C=12, N=14, Cl=35.5]$ (in $g$)

The correct sequence of reagents for the following transformation is:

$(a) \, CH_3CONH_2 + KOH + Br_2 \rightarrow$
$(b) \, CH_3COOH + \text{Soda lime} \rightarrow$
$(c) \, CH_3COOAg + Br_2 \rightarrow$
What is the common feature in the above three reactions?

How will you convert:
$(i)$ Ethanoic acid into methanamine
$(ii)$ Hexanenitrile into $1$-aminopentane
$(iii)$ Methanol to ethanoic acid
$(iv)$ Ethanamine into methanamine
$(v)$ Ethanoic acid into propanoic acid
$(vi)$ Methanamine into ethanamine
$(vii)$ Nitromethane into dimethylamine
$(viii)$ Propanoic acid into ethanoic acid?