Which of the following equations is non-linear?

The number of arbitrary constants in the general solution of a fourth-order differential equation is . . . . . . .

The order and degree of the differential equation $\left(\frac{d^3 y}{d x^3}\right)^{\frac{1}{2}}-2\left(\frac{d y}{d x}\right)^{\frac{1}{4}}+x y=0$ are respectively

Consider the following differential equations.
$D_1: y=4 \frac{dy}{dx}+3x \frac{dx}{dy}$
$D_2: \frac{d^2y}{dx^2}=\left(3+\left(\frac{dy}{dx}\right)^2\right)^{\frac{4}{3}}$
$D_3: \left[1+\left(\frac{dy}{dx}\right)\right]^2=\left(\frac{dy}{dx}\right)^2$
The ratio of the sum of the orders of $D_1, D_2$ and $D_3$ to the sum of their degrees is

The order and degree of the differential equation $\left[1+\left(\frac{dy}{dx}\right)^{3}\right]^{\frac{7}{3}}=7 \frac{d^{2}y}{dx^{2}}$ are respectively.

For the differential equation given below,determine its order and degree (if defined).
$\frac{d^{4} y}{d x^{4}}-\sin \left(\frac{d^{3} y}{d x^{3}}\right)=0$