What is the $IUPAC$ name of the compound $OHC-(CH_2)_2-CH(CHO)-(CH_2)_2-CHO$?

The $IUPAC$ name of the compound $CH_3-C(CH_3)=CH-CH_2OH$ is:

How many chiral carbon atoms are present in $2\text{-Iodo-}3,4,5\text{-trimethylhexane}$?

Write $IUPAC$ names and calculate the number of $\sigma$ and $\pi$ bonds for the following compounds:
$(i)$ $CH_3-CH(CH_3)-CH=CH-CH_2-CH=C(CH_3)-CH_2-CH_3$
$(ii)$ $CH_3-CH=CH-CH_2-CH=CH-CH(C_2H_5)-CH_2-CH_3$
$(iii)$ $CH_2=C(CH_2-CH_2-CH_3)_2$
$(iv)$ $CH_3-CH(C_4H_9)-CH=C(C_2H_5)-CH_2-CH(CH_3)_2$

Which of the following represents the correct $IUPAC$ name for the compounds concerned?
$(a)$ $2,2-$ Dimethylpentane or $2-$ Dimethylpentane
$(b)$ $2,4,7-$ Trimethyloctane or $2,5,7-$ Trimethyloctane
$(c)$ $2-$ Chloro$-4-$methylpentane or $4-$ Chloro$-2-$methylpentane
$(d)$ But$-3-$yn$-1-$ol or But$-4-$ol$-1-$yne

The $IUPAC$ name of $CH_3-CH=CH-C\equiv CH$ is