Answer
$x=2$ ($\lim\limits_{x \to 2} f(x)$ doesn't exist)
$x=3$ ($f$ undefined)
$x=4$ ($\lim\limits_{x \to 4} f(x)\not=f(4)$)
Work Step by Step
The function has discontinuities in the points:
$x=2$
$x=3$
$x=4$
In the point $x=2$, $\lim\limits_{x \to 2} f(x)$ doesn't exist, therefore Condition 2 is violated.
In the point $x=3$, $f$ is undefined, therefore Condition 1 is violated.
In the point $x=4$, $\lim\limits_{x \to 4} f(x)\not=f(4)$, therefore Condition 3 is violated.