The following is stated as an exercise in the "Classical Potential Theory" of Armitage and Gardiner (pg 195). Let $K$ be a compact of $\mathbb{R}^m$ ($m\geq2$) and $\Omega$ an open containing $K$. Suppose each bounded component of $\mathbb{R}^m\setminus K$ contains a point of $\mathbb{R}^m\setminus \Omega$. If $u$ is superharmonic on a neighborhood of $K$, then $u$ can be extended to a superharmonic function $\overline{u}$ whose restriction to $K$ equals $u$. I have two questions:

1. Do you have any idea of the proof?

2. Suppose $K$ is the boundary of a bounded open set $V$ and let $z\in V$. Let $\Omega$ be a neighborhood of the closure of $V$ from which we take off the point $z$. By the above result, if $u$ is a superharmonic function on a neighborhood of $K$, then $\overline{u}$ is superharmonic on $\Omega$. My question is: can we arrange that $$-\infty<\liminf \overline{u}(x),$$ as $x\to z$ from inside $\Omega$?