What will be the phase difference of particles in successive intervals of stationary waves?

The ends of a stretched wire of length $L$ are fixed at $x = 0$ and $x = L.$ In one experiment,the displacement of the wire is ${y_1} = A\sin (\pi x/L)\sin \omega t$ and energy is ${E_1}$,and in another experiment its displacement is ${y_2} = A\sin (2\pi x/L)\sin 2\omega t$ and energy is ${E_2}$. Then

$A$ standing wave is established in a single loop. At $t = 0$,the kinetic energy $(K.E.)$ of the string is zero. Choose the correct option.

$A$ wave is reflected from a rigid support. The change in phase on reflection will be

The phase difference between the two particles situated on both the sides of a node in a stationary wave is ... $^o$.

Which is the most important property of a stationary wave?