In the aqueous phase,what is the correct order of basic strength for methyl-substituted amines?

Assertion : Aniline is a better nucleophile than anilinium ion.
Reason : Anilinium ion has a positive charge.

The reaction of $HNO_2$ with $A$ gives a quaternary ammonium salt. $A$ is

In the following compounds,the order of basicity is:
$I$: Piperidine
$II$: Pyridine
$III$: Morpholine
$IV$: Pyrrole

The major product $B$ in the following reaction sequence is:
$CH_3-CH_2-CH(CH_3)-CONH_2$ $\xrightarrow{Br_2/KOH, \Delta} (A)$ $\xrightarrow{(1) CH_3I (excess), (2) AgOH/\Delta} (B)$

$A$ student performed an analysis of an aliphatic organic compound '$X$' which,upon analysis,gave $C=61.01\%$,$H=15.25\%$,$N=23.74\%$. This compound,on treatment with $HNO_2/H_2O$,produced another compound '$Y$' which did not contain any nitrogen atom. However,the compound '$Y$' upon controlled oxidation produced another compound '$Z$' that responded to the iodoform test. The structure of '$X$' is: