Which of the following is a virus belonging to the retrovirus group?

Arrange the following statements regarding $AIDS$ in the correct chronological order of the infection process:
$(1)$ After entering the individual's body,the $HIV$ virus enters macrophages,where the viral $RNA$ genome replicates into viral $DNA$ with the help of the reverse transcriptase enzyme.
$(2)$ $HIV$ enters helper $T$-lymphocytes.
$(3)$ $HIV$ has an $RNA$ molecule as its genetic material.
$(4)$ Newly formed viruses are released into the blood and attack other helper $T$-lymphocytes.
$(5)$ Viral $DNA$ is incorporated into the host cell's $DNA$.

Assertion $A$: $AIDS$ is a severe,incurable,infectious,and fatal disease.
Reason $R$: $HIV$ causes deficiency of the immune system in the body.
Which option is correct for Assertion $A$ and Reason $R$?

At which stage of $HIV$ infection do the symptoms of $AIDS$ appear?

What is a healthy person who is infected with $HIV$ called?

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