When does the magnetic flux become zero?

The net magnetic flux through any closed surface is

$A$ square coil of area $10^{-2} \ m^2$ is placed perpendicular to a uniform magnetic field of intensity $10^3 \ Wb/m^2$. The magnetic flux through the coil is ........ $Wb$.

$A$ circular disc of radius $20 \text{ cm}$ is placed in a uniform magnetic field of induction $\frac{7}{22} \text{ Wb/m}^2$ in such a way that its axis makes an angle of $60^{\circ}$ with $\vec{B}$. The magnetic flux linked with the disc is $(\cos 60^{\circ} = 0.5)$ (in $\text{ Wb}$)

$VS$ is the unit of which physical quantity?

Consider a closed loop $C$ in a magnetic field as shown in the figure. The flux passing through the loop is defined by choosing a surface whose edge coincides with the loop and using the formula $\phi = \sum \vec{B}_i \cdot d\vec{A}_i$. Now,if we choose two different surfaces $S_1$ and $S_2$ having $C$ as their edge,would we get the same answer for the magnetic flux? Justify your answer.