Solution (source code)

= Solution

\b[False.] Take $\kappa=\aleph_0$, $\lambda=1$, and $\lambda'=2$. Then
$$
\boxed{\kappa^1=\aleph_0=\aleph_0^2.}
$$
For example the <Cantor pairing function> $\langle m,n\rangle=(m+n)(m+n+1)/2+n$ bijects $\mathbb N^2$ with $\mathbb N$. Thus the exponent increases strictly while the cardinal power remains the same. This counterexample is completely choice-free.