Which is the best oxidizing agent to oxidize $CH_3CH=CHCHO$ to $CH_3CH=CHCOOH$?

The structure of the starting compound $P$ used in the reaction given below is:

Calcium butanoate on heating followed by treatment with $1,2-$ethanediol in the presence of a catalytic amount of an acid,produces a major product which is

$A$ and $B$ in the following reaction are:

Predict the products formed when cyclohexanecarbaldehyde reacts with the following reagents:
$(i)$ $PhMgBr$ and then $H_3O^{+}$
$(ii)$ Tollens' reagent
$(iii)$ Semicarbazide and weak acid
$(iv)$ Excess ethanol and acid
$(v)$ Zinc amalgam and dilute hydrochloric acid

Which of the following cannot give a yellow $ppt.$ with $I_2/NaOH$?