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

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

The differential equation $\left( \frac{d^2y}{dx^2} \right)^2 - \left( \frac{dy}{dx} \right)^{1/2} = y^3$ has the degree

Statement $1$: The degrees of the differential equations $\frac{dy}{dx} + y^2 = x$ and $\frac{d^2y}{dx^2} + y = \sin x$ are equal.
Statement $2$: The degree of a differential equation,when it is a polynomial equation in derivatives,is the highest positive integral power of the highest order derivative involved in the differential equation; otherwise,the degree is not defined.

The degree of the differential equation $(1 + \frac{dy}{dx})^2 = (\frac{d^3y}{dx^3})^{1/3}$ is . . . . . . .

Determine the order and degree (if defined) of the differential equation $y''' + 2y'' + y' = 0$.