Which among the following molecules is non-polar?

Which of the following diagrams shows the correct change in the polarity of the bond?

Which of the following molecules have non-zero dipole moments?
$I$. Gauche conformation of $1, 2$-dibromoethane
$II$. Anti conformation of $1, 2$-dibromoethane
$III$. Trans-$1, 4$-dibromocyclohexane
$IV$. Cis-$1, 4$-dibromocyclohexane
$V$. Tetrabromomethane
$VI$. $1, 1$-dibromocyclohexane

Which bond angle $\theta$ would result in the maximum dipole moment for the triatomic molecule $YXY$?

Which of the following has a dipole moment of zero?

The order of dipole moments of the following molecules is