In the given figure,what do $A$ and $B$ represent respectively?

Identify the correct sequence for the mechanism of $HIV$ infection:
$1.$ Viral $RNA$ replicates to form viral $DNA$ with the help of reverse transcriptase.
$2.$ The progeny viruses released in the blood attack other $T_H$ cells and destroy them.
$3.$ Viral $DNA$ gets incorporated into the host cell's $DNA$ and produces virus particles.
$4.$ Virus enters into macrophages.

Which of the following viruses contains the enzyme reverse transcriptase?

Which of the following statements is correct regarding $AIDS$?

Which disease is caused by the microorganism shown in the given figure?
$(2)$ What does the part labeled $(A)$ in the given figure represent?

Provide the full forms of the following abbreviations:
$(i)$ $DNA$
$(ii)$ $AIDS$