Which of the following waves has the largest wave speed?

The figure represents the instantaneous snapshot of a transverse harmonic wave traveling along the negative $x$-axis. Choose the correct alternative(s) related to the movement of the points shown in the figure. The point(s) moving downwards is/are:

$A$ wave is represented by $x = 4 \cos \left(8t - \frac{y}{2}\right)$,where $x$ and $y$ are in $m$ and $t$ is in $s$. The frequency of the wave (in $s^{-1}$) is .........

$A$ transverse wave is given by $y = A \sin 2\pi \left( \frac{t}{T} - \frac{x}{\lambda} \right)$. The maximum particle velocity is equal to $4$ times the wave velocity when:

$A$ sinusoidal wave of frequency $500 \,Hz$ has a speed of $350 \,m/s$. The phase difference between two displacements at two points separated by a distance of $1 \,m$ is ...........

$A$ transverse wave given by $y=2 \sin (0.01 x+30 t)$ moves on a stretched string from one end to another end in $0.5 \ s$. If $x$ and $y$ are in $cm$ and $t$ is in $s$,then the length of the string is: (in $m$)