An object is placed at a distance $2f$ from the pole of a curved mirror of focal length $f$. 

For a concave mirror, when object is placed at $2F$ (or $C$) real image of the same size as that object is formed at $2F$ (or $C$).

$\Rightarrow m_{\text{concave }}=\frac{-f}{-f-(-2f)}=-1$

For Convex mirror, 

$\Rightarrow m_{\text{convex }}=\frac{f}{f-(-2f)}=\frac{1}{3}$

Hence, $\left(2\right)$ and $\left(3\right)$ are correct.