Which of the following substances will not give a yellow precipitate with $I_2/NaOH$?

Consider the following sequence of reactions:
Isopropyl benzene $\xrightarrow{O_2} x$ $\xrightarrow[H_2 O]{H^{+}} y + z$
The incorrect statement about $z$ is:

$CH_3-CH(OH)-CH_2-CHO$
$3HCHO + A \xrightarrow[40^o C]{Na_2CO_3} (B) (82\%)$
Product $(B)$ of the above reaction is

Clemmensen's reduction will convert cyclohexanone into

Identify an aldehyde used in margarine and in food for its buttery odour.

An organic compound $CH_3-CH=CH-CH_2-CHO$ is taken in two different containers $A$ and $B$. Sample in $A$ is treated with $H_2 / Ni$ forming new compound $P$. Sample in $B$ is treated with $LiAlH_4$ and hydrolyzed further forming new compound $Q$. Identify $P$ and $Q$.