While antacids and antiallergic drugs interfere with the function of histamines,why do these not interfere with the function of each other?

Chemically,heroin is:

Match List-$I$ with List-$II$.

List-$I$ (Antimicrobials)	List-$II$ (Names)
$A$. Narrow spectrum antibiotic	$I$. Furacin
$B$. Antiseptic	$II$. Sulphur dioxide
$C$. Disinfectants	$III$. Penicillin-$G$
$D$. Broad spectrum antibiotic	$IV$. Chloramphenicol

$A$ chemist has $4$ samples of artificial sweetener $A, B, C$,and $D$. To identify these samples,he performed certain experiments and noted the following observations:
$(i)$ $A$ and $D$ both form blue-violet colour with ninhydrin.
$(ii)$ Lassaigne extract of $C$ gives positive $AgNO_{3}$ test and negative $Fe_{4}[Fe(CN)_{6}]_{3}$ test.
$(iii)$ Lassaigne extract of $B$ and $D$ gives positive sodium nitroprusside test.
Based on these observations,which option is correct?

Which of the following is an anti-diabetic drug?

$A$ $16$-year-old boy visits a doctor complaining of sneezing,watery eyes,and a runny nose,along with constant itching in the eyes. He also has a known allergy to dust. Which medicine will the doctor recommend?