$1$ S$1$: Perceptron is a two layer network and weights of both layers' neurons are trainable

S$2$: The input applied to first layer lies in image space and its output forms pattern space.

S$3$: It is necessary to make the input patterns to be linear separable before applying to second layer.

S$4$: The solution obtained on convergence by each perceptron is always unique.

True Statements $($out of $$\frac{1}{\text{\$}}\frac{2}{S}\frac{3}{S}4)$ are$-$