1.) $1$
2.) Does not exist, since $\log(0)$ is undefined.
3.) $\pi$
4.) $1$
5.) Nothing. Knowing those two limits tells you nothing about the one in two variables -- it does not exist.
6.) It is continuous everywhere except on the line $y = e^{\frac{x}{2}}$.
7.) It is continuous everywhere except for where $y < 0$. Another way to say this is that it is "continuous on the upper half-plane" (including the $x$-axis).
8.) $1$
9.) Does not exist. Approaching $(0,0)$ along the line $y=x$, you get a limit of $\frac{1}{2}$ but along the line $y=2x$ you get a limit of $\frac{1}{5}$.