The number of chiral centres present in $[B]$ is

Which of the following statements is correct regarding the given compounds $(1)$,$(2)$,and $(3)$?

In the projection formula $[A]$,two groups ($Br$ and $CH_3$) at the chiral center are interchanged to obtain formula $[B]$. When two groups ($C_2H_5$ and $Cl$) of $[A]$ are interchanged,the projection formula $[C]$ is obtained. Which of the following statements is $NOT$ correct for $[A]$,$[B]$,and $[C]$?

The compound $C_{4}H_{10}O$ can show which of the following types of isomerism?

The correct statement$(s)$ concerning the structures $E, F$ and $G$ is (are):
$E$: $CH_3CH_2CH(CH_3)COCH_3$
$F$: $CH_3CH_2C(OH)=C(CH_3)_2$ (enol form)
$G$: $CH_3CH_2C(CH_3)=C(OH)CH_3$ (enol form)
$(A)$ $E, F$ and $G$ are resonance structures
$(B)$ $E, F$ and $E, G$ are tautomers
$(C)$ $F$ and $G$ are geometrical isomers
$(D)$ $F$ and $G$ are diastereomers

How many chiral carbon atoms are present in $2-$Bromo$-3, 4, 5-$trimethylhexane?