What is the $IUPAC$ name of the following compound?

What is the $IUPAC$ name of $CH_3-CH_2-CH=C(CH_3)CH_2OH$?

Structures and $IUPAC$ names of some hydrocarbons are given below. Explain why the names given in the parentheses are incorrect.
$(a)$ $CH_3-CH(CH_3)-CH_2-CH_2-CH(CH_3)-CH(CH_3)-CH_2-CH_3$
Name: $2,5,6-$Trimethyloctane [and not $3,4,7-$Trimethyloctane]
$(b)$ $CH_3-CH_2-CH(CH_2CH_3)-CH_2-CH(CH_3)-CH_2-CH_3$
Name: $3-$Ethyl$-5-$methylheptane [and not $5-$Ethyl$-3-$methylheptane]

The compound which has one isopropyl group is

Which of the following is the correct $IUPAC$ name for the compound $CH_3-CH(CH_3)-CH_2-CH(CH_3)-CH_3$?

The $IUPAC$ name of the following compound is