What is the normal count of $CD_4$ cells in a healthy human?

The full form of $AIDS$ is:

In which of the following situations is $AIDS$ $NOT$ transmitted?

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 $DNA$.

The time interval between the infection and the appearance of $AIDS$ symptoms is usually ...........

Which tests are used for the diagnosis of $AIDS$?