Stereoisomers which are not the mirror images of one another are called

How many optical isomers are possible for a compound having $3$ asymmetric carbon atoms?

Which of the following statements is not true about enantiomers?

$CH_3 - CHCl - CH_2 - CH_3$ has a chiral center. Which one of the following represents its $R$-configuration?

Optically active $(S)-2-$methoxypropanal on reaction with $MeMgX$ gives a mixture of alcohols. The major diastereomer $P$ on treatment with $MeI / K_2CO_3$ gives an optically inactive compound. $P$ is

$A$ natural product was isolated in the laboratory and its observed rotation was $+10^{\circ}$. When measured in a $1 \ dm$ sample tube containing $1 \ g$ of compound in $10 \ mL$ of water. What is the specific rotation of this compound?