(i)
Acidity depends on the stability of the conjugate base.  In the case of amine, the negative charge is on the N-atom whereas, an alkoxide ion, the negative charge is on the O-atom.

Since O is more electronegative than N, O can accommodate the negative charge more easily than N.
As a result, the amide ion is less stable than the alkoxide ion. Hence, amines are less acidic than alcohols of comparable molecular masses.

(ii) 
In a molecule of a tertiary amine, there are no H−atoms whereas in primary amines, two hydrogen atoms are present. Due to the presence of H−atoms, primary amines undergo extensive intermolecular H−bonding. 

As a result, extra energy is required to separate the molecules of primary amines. Hence, primary amines have higher boiling points than tertiary amines.

(iii)
Due to the −R effect of the benzene ring, the electrons on the N- atom are less available in the case of aromatic amines. Therefore, the electrons on the N-atom in aromatic amines cannot be donated easily. 

But in the case of aliphatic amines, +I effect of the alkyl group increases the electron density in the nitrogen atom   This explains why aliphatic amines are stronger bases than aromatic amines.