Predict the product when the given compound $(A)$ reacts with $NaBH_4$.

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

Which of the following would undergo aldol condensation?

Which of the following organic compounds exhibits positive Fehling test as well as iodoform test?

Which of the following transformations can be achieved using $Wolff-Kishner$ reduction conditions?

In the reaction scheme shown below,$Q$,$R$,and $S$ are the major products. Identify the correct structure of the products from the given options:
$(P)$ + Succinic anhydride $\xrightarrow{AlCl_3}$ $Q$
$Q$ $\xrightarrow[H_3PO_4]{Zn-Hg/HCl}$ $R$
$R$ $\xrightarrow[(ii) H_3O^+]{(i) CH_3MgBr, (iii) H_2SO_4/\Delta}$ $S$
$(A)$ $S$ is [Structure $A$]
$(B)$ $Q$ is [Structure $B$]
$(C)$ $R$ is [Structure $C$]
$(D)$ $S$ is [Structure $D$]